The Watch Site banner

1 - 20 of 33 Posts

·
Registered
Joined
·
25,442 Posts
Re: Does anyone know the definitive answer to the "X".."J" Japan marks on case backs

Definitive, I truthfully can't say, But a while back I did an exhaustive look into this and came up with the different letters stand for the different Seiko factory locations. That's my story and I'm sticking to it :)
 

·
Administrator
Joined
·
29,486 Posts
Discussion Starter #3
Re: Does anyone know the definitive answer to the "X".."J" Japan marks on case backs

DAHASCO said:
Definitive, I truthfully can't say, But a while back I did an exhaustive look into this and came up with the different letters stand for the different Seiko factory locations. That's my story and I'm sticking to it :)
Did you definitively place a factory and location to each letter during your exhaustive look into this. :)
 

·
Banned
Joined
·
2,569 Posts
Re: Does anyone know the definitive answer to the "X".."J" Japan marks on case backs

TheTigerUK said:
or any of the various others, Is it a production code, production plant or..............
If you are actually asking about 'K' vs 'J'; may never know' definitively.

Seiko itself has two conflicting stories; yserv says that the letters only indicate distribution channels while JakeB's Seiko salesmen claim otherwise.

Personally; I don't see the business sense of producing two identical entry level watches in two different locations where the production costs are so different.

Until solid proof is provided; I will go with the yserv version...it just makes sense ;)
 

·
Registered
Joined
·
25,442 Posts
Re: Does anyone know the definitive answer to the "X".."J" Japan marks on case backs

TheTigerUK said:
Did you definitively place a factory and location to each letter during your exhaustive look into this. :)

John, By "exhaustive" I mean what I could find online, No factory/location coloration was found, Only speculation :(
 

·
Banned
Joined
·
5,181 Posts
Re: Does anyone know the definitive answer to the "X".."J" Japan marks on case backs

what are there....


J, X, A, Z, B, U, L, M... that's just from a quick mental survey plus checking the various watches on the desk here...


I've only seen "Z" on bracelets I think..


OK, here's what I have right in front of me:


7005-8072 Jan 71 - M
6119-6023 Aug 72 - F
6119-6023 Apr 74 - F
7006-7199 Nov 73 - L
6106-8589 Jan 71 - U
6119-6400 May 74 - A
7549-7010 Dec 79 - A
6119-5000 Sep 71 - A
6139-6002 Jul 72 - J
6139-6002 Jan 76 - J
6139-8020 Jan 72 - A
6139-8002 Sep 72 - J
6139-6001 Nov 70 - J
6139-8010 Dec 72 - J
6139-6011 Oct 70 - A
6139-6005 Sep 75 - J
6119-8490 Feb 72 - A


I have another 50 or so watches - the only pattern I see here is that the same models seem to carry the same code, even if they are made in separate years. Anyway, I'd be happy to do the data entry on everything here if that would help, as long as we're not reinventing the wheel - has anyone else carried out this kind of survey?
 

·
Registered
Joined
·
201 Posts
Re: Does anyone know the definitive answer to the "X".."J" Japan marks on case backs

Pin said:
Personally; I don't see the business sense of producing two identical entry level watches in two different locations where the production costs are so different.
I see this in my business all the time - typically they do this to save on import taxes and to have protection from a disaster knocking out one of their plants.
 

·
Administrator
Joined
·
29,486 Posts
Discussion Starter #8
Re: Does anyone know the definitive answer to the "X".."J" Japan marks on case backs

hankaarons said:
I see this in my business all the time - typically they do this to save on import taxes and to have protection from a disaster knocking out one of their plants.
We also used to do this often in my old job has high volume engine component makers, we were on penalty clauses if we failed to supply on any given day and for us not so much a worry about natural disasters but more plant break downs, power cuts, personnel and mudane things like that, so certain critical component we would produce at a couple of our sites just to be on the safe side.
 

·
Registered
Joined
·
2,201 Posts
Re: Does anyone know the definitive answer to the "X".."J" Japan marks on case backs

With combined forces, it MUST be possible to eventually solve this mystery!!
I know the 'Japan X' issue has been discussed for years, let's find the solution!

To begin, I know of three hypotheses of what the engravement could refer to:

1. it refers to the case construction
2. it refers to material quality/a certain production process
3. it refers to a certain plant/production line within a plant

I will try to discuss each hypothesis based on the Seiko documentation I have available and based on the preliminary outcome of my little Bell-Matic 'research' project (my caseback database currently contains approx. 600 unique case (sub)number/serial number entries). Attached is an excerpt from a Seiko Case Servicing Guide, issued April 1982 by Seiko technical department NY.

Hypothesis 1:
On the bottom of the page, you can see that they claim that 'Japan R' is not a case construction marks, but a 'Factory production code' - what ever this means. And concerning Bell-Matics: Pre March 1968 models (7000, 7010/7019 and 7020/7029) do not have a 'Japan X' engravement on the caseback, but rather on the inside of the caseback. Thus it makes little sense that the mark refers to a case construction - or the watchmaker would only know once the watch has already been opened. Hypothesis 1 can thus in my opinion be rejected.

Hypothesis 2:
This hypothesis was raised in a Spanish watch forum while discussing Seiko bracelets. There, it was stated, that the mark refers to a certain steel quality or manufacturing process - with 'Z' being the most durable. The original bracelets on my Seikos often carry a 'Z' mark in the clasp, however, e. g., the 6117-6400/10 'Railroad' or 6138-300x bracelets are marked 'B' - so it could be possible. Also, this hypothesis is not necessarily contradicted by the statement in the case servicing guide. Bell-Matics: my database contains just about EVERY submodel that was ever talked about or is contained in a Casing guide (except: 4005-7001 and 4006-7025).

1. ALL 700x and 702x submodels in my database carry a 'Japan J' mark - thoughout the whole production period from Nov1966 to Dec1978.
2. ALL the remaining models including 4005 carry a 'Japan A' mark. There is not a single caseback out of 600 - irrespective of the case material (SS or SGP) and the case subnumber - that contradicts this.

Thus, the Bell-Matic data do also not contradict that theory.

Hypothesis 3:
The observations for hypothesis 2 are also valid for this hypothesis. However, there is an additional observation that I made:
As most of you know, the Serial Number of Vintage Seikos was changed from a 7-digit to a 6-digit code.

Concerning the 4006-7000 model, the 6-digits were first used in July 1967. The 4006-7020 model was introduced in September 1967 according to my DB - and it never carried a 7-digit SN. HOWEVER, the 4006-7010 model was manufacured AT LEAST until January 1968 with a 7-digit SN.

So why the different SN change dates? Well, as I said before - both 7000 and 7020/7029 models carry a 'Japan J' mark, while the 7010/7019 models carry a 'Japan A' mark.

A plausible explanation for this would thus be, that the model series where manufactured at different plants/production sites/manufacturing lines, and while one line changed the SN system in July 1967, the other one did so in February 1968.

I am thus of the opinion, that only hypothesis 3 is valid - and that the 'Japan X' designation refers to a plant/production site/manufacturing line ONLY. However, I do not yet have a theory what the individual letters stand for - to be continued :)

Best,
Hermann
 

Attachments

·
Registered
Joined
·
1,140 Posts
Re: Does anyone know the definitive answer to the "X".."J" Japan marks on case backs

I think it's just another sadistic attempt by the Nipponese to take over the world by driving the height-unchallenged Americans slowly further out of their minds with unanswered questions of the Universe better left unknown, thus reducing Americans' stature in the world to that of all the more reasonably fed countries!!! ...and, I'm sticking to my explanation!!! :)) :)) :)) :)) :)) :)) :)) :)) :)) :)) :))
 

·
Registered
Joined
·
2,201 Posts
Re: Does anyone know the definitive answer to the "X".."J" Japan marks on case backs

That is why there are also Europeans contributing in this post

;)

Best,
Hermann
 

·
Registered
Joined
·
1,140 Posts
Re: Does anyone know the definitive answer to the "X".."J" Japan marks on case backs

Euro... what??? :D :D :D :D I didn't know there was anywhere else other than Japan and America. ^-^ :)) Are y'all grossly overfed and too large, too? :))
 

·
Administrator
Joined
·
29,486 Posts
Discussion Starter #13
Re: Does anyone know the definitive answer to the "X".."J" Japan marks on case backs

StartSomething said:
1. ALL 700x and 702x submodels in my database carry a 'Japan J' mark - thoughout the whole production period from Nov1966 to Dec1978.
2. ALL the remaining models including 4005 carry a 'Japan A' mark. There is not a single caseback out of 600 - irrespective of the case material (SS or SGP) and the case subnumber - that contradicts this.

Thus, the Bell-Matic data do also not contradict that theory.


Best,
Hermann
Good research Herman and all my Belles follow the same rule.

Strange that the 4006-7010 carries the "A" with all the other 70XX having the "J".
 

·
Registered
Joined
·
9,869 Posts
Re: Does anyone know the definitive answer to the "X".."J" Japan marks on case backs

TheTigerUK said:
Good research Herman and all my Belles follow the same rule.

Strange that the 4006-7010 carries the "A" with all the other 70XX having the "J".

Yes, interesting... and Belle Diashocks have no "Japan" at all.... (also noticed this on other 7-digit serial number Bell-matics)
 

·
Registered
Joined
·
2,201 Posts
Re: Does anyone know the definitive answer to the "X".."J" Japan marks on case backs

John,

yes, they do:

:)

StartSomething said:
Pre March 1968 models (7000, 7010/7019 and 7020/7029) do not have a 'Japan X' engravement on the caseback, but rather on the inside of the caseback. Thus it makes little sense that the mark refers to a case construction - or the watchmaker would only know once the watch has already been opened. Hypothesis 1 can thus in my opinion be rejected.
Sorry, my post was obviously a little bit too long ;-)

Best,
Hermann
 

·
Registered
Joined
·
9,869 Posts
Re: Does anyone know the definitive answer to the "X".."J" Japan marks on case backs

Sorry, I missed that reference, Hermann. :banghead:


StartSomething said:
John,

yes, they do:

:)

Sorry, my post was obviously a little bit too long ;-)

Best,
Hermann
 

·
Registered
Joined
·
9,869 Posts
Re: Does anyone know the definitive answer to the "X".."J" Japan marks on case backs

TheTigerUK said:
JohnN what marking is on that 66 case back of yours ?

Never had the caseback off. it is so pristine that I fear my asleep brain will result in a demoralizing scratch.
 

·
Registered
Joined
·
9,869 Posts
Re: Does anyone know the definitive answer to the "X".."J" Japan marks on case backs

By all means! Does "our" Biz Belle have the J?


TheTigerUK said:
I have just checked it for you John, if i may have your permission to post this picture ?

It is a "J"

 
1 - 20 of 33 Posts
Top