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Discussion Starter #1
Hi All,

I'm looking for some information on the Seiko Sportsmatic Calendar 820.

I picked this one up (photos attached) on recent trip to Tokyo from a shop in Nakano Broadway. I was aware of the Seiko Sportsmatic line but had never seen this specific model. I was assured it was all original besides the strap (Japanese sellers are helpful and upfront so I have no reason to doubt this) and bought it at a good price.

My online research so far shows that it was manufactured in 1971 based on the production run of the Cal. 820 but it has the aesthetics of a 60's Seiko dress watch which is interesting.

Most of my searches returned information on the more sportier/popular Sportsmatics like the "Silver Wave" and other Water Proof versions. I have been unable to find any catalog listings or literature on this specific version and would be grateful for any information!

Thanks in advance
 

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Very nice looking watch, I'd say 1961 based on the design?
Thanks. The seller told me it was from 1971 and my research shows that the Cal. 820 was manufactured from 1964 - 1974. Other than that I can't seem to find much literature on this watch.
 

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The 150400D is the model. You need to take the caseback off and the serial number should be on the inside of the caseback.

Not mine, a pic from the internet as an example
 

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The 150400D is the model. You need to take the caseback off and the serial number should be on the inside of the caseback.

Not mine, a pic from the internet as an example
All information is appreciated! Thanks.

I did find the printed "serial number" on the case back a bit odd. With this info it is possible that the watch could have been made in the mid-late 60's. It shall remain a mystery for now as I don't intend on opening the back anytime soon.

Another point of interest is the model numbering format. Very different from the usual xxxx - xxxx model numbering.
 

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The 150400D is the model. You need to take the caseback off and the serial number should be on the inside of the caseback.

Not mine, a pic from the internet as an example
I think I found the listing online for the photo you attached. Seller is saying his model is from 1963. Again back to the same issue of when the Cal. 820 (or 7625A) was released. The Seiko date calculator I posted earlier shows 1964 - 1974.

Would be nice to get some clarity on the Cal. 820.
 

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All information is appreciated! Thanks.

I did find the printed "serial number" on the case back a bit odd. With this info it is possible that the watch could have been made in the mid-late 60's. It shall remain a mystery for now as I don't intend on opening the back anytime soon.

Another point of interest is the model numbering format. Very different from the usual xxxx - xxxx model numbering.
It will most likely be from 1963 or 1964. Seiko started switching to the xxxx-xxxx model number format starting in around 1964. This previous model number format which they used from the mid-1950s to around 1963 has the first 2 numbers indicating the dial diameter in lignes. You can tell if the model number is in this format, because there will be 5 numbers, with the first 2 numerical digits being in the tens, between 10 and 16. 1 ligne = 2.2558291 mm, so 15 lignes = ~33.84 mm. The diameter of the watch will be roughly that plus the width of the bezel on each side. Some watches have a “J” prefixed to the number, which indicates an additional half-ligne to the number following it. The largest number I have seen in this system is J16. The following digits are the case style, which may be followed by 1 or 2 letters, which also form part of the case style designation. You can also tell by the pre-Grammar-of-Design style of the watch. 820 is the old 3-digit calibre number - Seiko also started switching to the new 4-digit calibre numbers (7625 in this case) around 1964.

https://en.wikipedia.org/wiki/Ligne

I think I found the listing online for the photo you attached. Seller is saying his model is from 1963. Again back to the same issue of when the Cal. 820 (or 7625A) was released. The Seiko date calculator I posted earlier shows 1964 - 1974.

Would be nice to get some clarity on the Cal. 820.
The serial number in that photo beginning in "3D" indicates that the case serial number was stamped in December 1963. The Trovestar source is more reliable than that Seiko date calculator.

Thanks for that.

Gonna have to search some 60's catalogues to get more details!
Here is a 1963 catalogue showing the watch:

https://www.thewatchsite.com/13-ads-catalogs-vintage-current/214681-seiko-brochures-1960-s.html#post1695921

Here are the later 1960s catalogues, which show that by 1966/1967, they now have Grammar of Design-style cases, and the later style model numbers: https://www.plus9time.com/blog/2019/5/11/seiko-watch-catalogs-late-1960s-jdm
 

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Discussion Starter #14
It will most likely be from 1963 or 1964. Seiko started switching to the xxxx-xxxx model number format starting in around 1964. This previous model number format which they used from the mid-1950s to around 1963 has the first 2 numbers indicating the dial diameter in lignes. You can tell if the model number is in this format, because there will be 5 numbers, with the first 2 numerical digits being in the tens, between 10 and 16. 1 ligne = 2.2558291 mm, so 15 lignes = ~33.84 mm. The diameter of the watch will be roughly that plus the width of the bezel on each side. Some watches have a “J” prefixed to the number, which indicates an additional half-ligne to the number following it. The largest number I have seen in this system is J16. The following digits are the case style, which may be followed by 1 or 2 letters, which also form part of the case style designation. You can also tell by the pre-Grammar-of-Design style of the watch. 820 is the old 3-digit calibre number - Seiko also started switching to the new 4-digit calibre numbers (7625 in this case) around 1964.

https://en.wikipedia.org/wiki/Ligne



The serial number in that photo beginning in "3D" indicates that the case serial number was stamped in December 1963. The Trovestar source is more reliable than that Seiko date calculator.



Here is a 1963 catalogue showing the watch:

https://www.thewatchsite.com/13-ads-catalogs-vintage-current/214681-seiko-brochures-1960-s.html#post1695921

Here are the later 1960s catalogues, which show that by 1966/1967, they now have Grammar of Design-style cases, and the later style model numbers: https://www.plus9time.com/blog/2019/5/11/seiko-watch-catalogs-late-1960s-jdm
Spot on! Thank you ever so much for that. Brings my search to an end. I agree that it is most likely an early-mid 60's watch based on the information you've provided.

Amazing to see that it was a lower-mid tier watch in the Seiko catalogue. The design and build quality (including the movement accuracy) punch well above its price tag. Much like the modern SARB series.

Now to find a reasonably priced Sportsmatic Silver Wave!
 

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Discussion Starter #15
It will most likely be from 1963 or 1964. Seiko started switching to the xxxx-xxxx model number format starting in around 1964. This previous model number format which they used from the mid-1950s to around 1963 has the first 2 numbers indicating the dial diameter in lignes. You can tell if the model number is in this format, because there will be 5 numbers, with the first 2 numerical digits being in the tens, between 10 and 16. 1 ligne = 2.2558291 mm, so 15 lignes = ~33.84 mm. The diameter of the watch will be roughly that plus the width of the bezel on each side. Some watches have a “J” prefixed to the number, which indicates an additional half-ligne to the number following it. The largest number I have seen in this system is J16. The following digits are the case style, which may be followed by 1 or 2 letters, which also form part of the case style designation. You can also tell by the pre-Grammar-of-Design style of the watch. 820 is the old 3-digit calibre number - Seiko also started switching to the new 4-digit calibre numbers (7625 in this case) around 1964.

https://en.wikipedia.org/wiki/Ligne



The serial number in that photo beginning in "3D" indicates that the case serial number was stamped in December 1963. The Trovestar source is more reliable than that Seiko date calculator.



Here is a 1963 catalogue showing the watch:

https://www.thewatchsite.com/13-ads-catalogs-vintage-current/214681-seiko-brochures-1960-s.html#post1695921

Here are the later 1960s catalogues, which show that by 1966/1967, they now have Grammar of Design-style cases, and the later style model numbers: https://www.plus9time.com/blog/2019/5/11/seiko-watch-catalogs-late-1960s-jdm

By the way, Thanks for the reference sites. Appreciate the sharing of information and literature. I'm new to using forums and don't know how to award points for responses! Sorry.
 

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Different type of movement, but I removed the back of my Seikomatic. You can see the model number, as mentioned by Zeke441, on the inside and barely visible on the outside, and the actual serial number on the inside. I'll have to re check all my old seiko watches :)
 

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Different type of movement, but I removed the back of my Seikomatic. You can see the model number, as mentioned by Zeke441, on the inside and barely visible on the outside, and the actual serial number on the inside. I'll have to re check all my old seiko watches /images/smilies/smiley.gif
Nice. I'm becoming increasingly tempted to open the back haha.

Sportsmatics are awesome. Was surprised to find that this was a lower - mid level Seiko for its time. It has aged incredibly well.
 
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