Project Restoration/Build - 68 Seiko 5126-8090 70m Proof aka Kamen Rider

Been a while since I have posted any restoration and service content for you guys and it has also been a while since I last worked on a Seiko cal 5126. What an interesting and challenging movement to work on. Produced in the late 60s, these movements appear to be a transitional period for Seiko with more Swiss like architecture in this design prior to Seiko moving to their magic lever self winding mechanism. By comparison, the 5126 autowinding mechanism sits in a package of gears housed along side the train and barrel assembly versus the traditional place on top of the barrel bridge. A complex stacked reversing gear in the auto winding mechanism allows for winding in both directions.

This watch presented in worn but good condition overall with beautiful numbers matching dial and case back. Dial and hands were in excellent condition. The SCWF member (Larry) provided an OE bezel and retaining spring for this watch. The bracelet on this watch is very interesting. I assume it is OE, but I am not familiar enough with this model to say yes or no. Other than new seals and crystal on the case, it was left unpolished. The seals in the watch were badly perished and the crystal seal which are usually soft and pliable on these 50+ year old watches was hard as a rock. I actually had to break out and use my crystal press to get the crystal free from the case. The bracelet was treated to cleaning and conservative refinishing.

The cal 5126 movements was treated to a strip down, cleaning, inspection, and re-assembly with modern lubricant. No issues found. Good amplitude and timing following service. A beautiful and rarely seen vintage Seiko. Thanks for looking.

Cal 5126 Disassembly:



Complex Keyless Works: 5126 utilizes quickset for date only. Advancement of the day can only be accomplished by moving the hands through midnight. Keyless and Day/Date quickset greatly simplified in later 6139/6138 series movements.


Crystal Removal - Kamen Rider uses the same 320W10GN00 crystal used in the 6105 divers. This one appeared to have the same profile height as a Type III low profile crystal so that is what I used on the replacement.

Underside of the Train Bridge. Note integrated gears on the underside to interact with the auto winding bridge and gear setup.

Center Wheel Bridge and Screws: Believe it or not, these screws are similar to those used on the pallet bridge but with a lower profile head. They can't be interchanged. If you use the incorrect pallet cock screw on the center wheel bridge, the head of the screw will extend above the top of the center wheel bridge and cause interference. Lesson learned from servicing one of these movements a few years back that required me to have to tear the entire train side down to change out these screws.

Case Assembly w New Seals and Crystal. Bracelet Refinished.