Here is a repost of my entrypost on the old forum, thought it may come handy here:
Here it is, the SBDX011 aka Tuna can (it really says everything).
Monocoque titanium case, internal A/R coated sapphire crystal, ceramic bezel protection, 8L35 engine.
For anybody willing to continue reading, I'll start with the history. After its beginnings with divers in the 60's, Seiko creates a team with the objective to design a professional diver from scratch. Without any limitations (mental or technical), Seiko's engineers, lead by Mr.Tokunaga created the first Tuna in 1975, the 6159-022, propelled by a 6159 caliber,basically a high range Seiko beating at 36,000. This instrument was the result of more than 20 patents and "first time in a dive watch" like the titanium monocoque case, the ceramic protection, the L shaped gasket, the vented strap and so on. Here it is:
Photo found on the net
Another specific detail of this watch was the fact that it did not necessitate a he release valve due to the design of the case/gasket/crystal.
The models replacing the 6159-022 were all quartz driven until the SBDX001 (OK, there is the 005, but that was a L.E.) The characteristics are similar to the grandfather, but it cases a 8L35 movement, basically a Grand Seiko unelaborated movement (28,800 b/h, 26 jewels, "magic wheel" winding, etc.). Photos:
Photos found on the net
I was searching for a "different" diver and decided to get this Seiko, as in my opinion it represents a different approach to the professional divers. The care for details is fantastic, the workmanship on the details is extremely accurate (the ti case is kind of PVD-ed, do not know how Seiko calls it, but you need to see it in the flesh to appreciate it). The case protection is made of some kind of matte ceramic, fixed by four hex screws, also PVD-like treated (I suppose they are also made of Ti, but can't tell for sure). Even the usually lousy rubber strap is fantastic (not comparable to the one you get with a SKX007) as are the kind of PVD-ed buckle and keeper (btw both bearing Seiko name on them). Lume needs no comments. The hour and minute hands are also matte finished, while the second hand is not, hence popping out and being more visible. Titanium in this case does not help keeping the weight down, the watch IS massive and heavy.
Some more pics:
The dimensions of the watch are, er, big, as you can see from this pics with a PAM (sorry for the lousy pics, I made them in a hurry this morning):
I'll post some pics of the box later, sorry...
Since it has just arrived, I cannot comment on performance, but based on my experience with lower end Seiko I expect I'll be satisfied.
The watch is a fantastic piece, really well made. It is well above the Sumo, you can feel you are stepping in another range.
It may not be for everybody, few may like it,even fewer buy it, but it remains loyal to its function without shame.