1980s Seiko 5 Case Swap Validity

Hello! I’ve been planning on doing a case swap with a Seiko 5 from the 1980s (7S26-3180)

The movement is a pretty old one without some of the modern-day features and has broke down so I’m going to be upgrading it to a 7S36 or any other compatible equivalent (that maybe has hand winding unlike the 7S36).

Since I find the dial great for a field watch, I would want to keep the dial and hands (and also maybe a crown from another donor) to fit the 38mm DWC Expedition Case

Is this possible? Should I stick to the 7S36 or go with another movement? Where could I get a seiko crown from? Is there anything I have to be of concern of?

AFAIK the only thing you need to look out for is your 7s36 has the 4 o’clock crown, while the DWC case has a 3 o’clock crown. As a result the day date will be slightly misaligned relative to the window.

Best option for you is to get a new NH36 movement with 3 o’clock crown (basically 7S36 with hackable second), get the case from DWC, keep the original dial and hand.

Don’t worry about the crown because the DWC case comes with a crown with precut stem.

Thanks for the advice! I also have more questions if you don’t mind answering:

Do I have to find a dial from a 38mm one instead of a 35mm one?
aftermarket day/date wheel
How hard would it be to replace the date/day wheel with an aftermarket one? How do I make it show the days in English instead of Japanese?

Replacing day/date wheel isn’t hard. You select the language the same way you select the date; it’s a half stop instead of a full stop. I’m a little concerns you’re using a tape measure instead of calipers though!!

I suspect the dials are the same, but it would be best to open it up and confirm. My google is failing my here. (I’m pretty sure they’re the same but it would be embarrassing to go through all the work and they’re not.)

The dial should be the same since it’s install onto the movement. The DWC page states that the dial diameter is 28.5mm. You can double check that.

The DWC Expedition case is wider in diameter because there is a chapter ring on it, and a suitable movement holder comes with the case. The same dial should fit.

On replacing the day/date wheel: make sure the replacement day/date wheel is for 3 o’clock crown as well. I recall that the wheel is responsible for the alignment between 3 o’clock vs 4 o’clock crown

I also made a mental mistake on the dial. The dial feet will fit but the dial will be tilted as well. A usual way to deal with this is to snip off the original dial feet and use dial dots (adhesive for dial). Or just get a replacement dial

I haven’t got the watch I’m stripping for the dial on my hands yet! Plus the case is so scratched up that I don’t really care.

I really like the Arabic dial the watch comes with so that’s why I wanted to do a case swap with the Seiko 5. If you have any suggestions on brands or watches that have a dial like the one I’m planning on using with compatible dial feet that is not above 400hkd feel free to. Of course I’m going to be checking DWC’s own dials made for the expedition case.

I’ll look into the dial dots for now just in case.