It depends on the size. I don’t think the date wheel is a 1:1 match for a 7s26 and a 4series or NH35. The date wheel and day wheel are separate pieces on movements.

There are solutions like buying date wheel overlays. Basically a decal (sticker) that has either different fonts or languages. Finding the vendor for this would be the first thing. Talking to Yobokies would be a step in the right direction as they seem to know where to get most things for modding Seikos if they don’t produce something.

Many expensive watches use overlays, so don’t be put off by that.


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For the 7S26 and the NH36 the day and date wheels are interchangeable. The differences arise in the day (Mon-Sund) wheels and dials depending on 3'o clock vs 4'o clock stem position.
Please see this site for a picture of the misalignment that happens with the day wheels : https://seikoparts.wordpress.com/2017/03/27/supercharge-your-skx007-with-a-nh35/

I've swapped a 3'o clock NH36 into an SNK809 case with 4'o clock stem, and had to swap the day wheel so it would align (swapped both wheels anyway so they would be black).

 

This is correct. Date wheel is the same for 7s and 4r in both 3 o clock and 4 o'clock crown positions.

Day wheel fits but is misaligned for 3 o'clock and 4 o'clock crown positions. You can order the correct day wheel on ebay.

I modded an skx and put a black day wheel in along with and Nh36.

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