I've had one of these for a while and written about it (and its brethren, here). In short, the JDM version of this watch didn't say SPORTS 100 on the dial, and had SPEEDMASTER engraved on the clasp, and was sold as part of a range of "SPEEDMASTER" watches. The 15-jewel 7a28 movement has no plastic parts, can be regulated and fully serviced, and was the world's first analogue quartz chronograph.



This one for sale, I acquired originally thinking that I might take a couple of bits off it and fit them to my other one (pictured in that thread linked in the opening line), but after cleaning it up, it's far too nice to break up like that. It's worn, but working. As can be deduced from the serial number (the first digit being the year in the decade, the 2nd being the month of that year), this watch was made in November 1983.

The crystal is quite probably original and has a few scratches, though nothing too noticeable on the wrist. Service history unknown, but everything works as expected (though the top right pusher is a little spongy in feel, it starts and stops the chrono fine). The bracelet is sized to about a 20cm wrist (7 3/4 inches) and has scuffs from wear.


It's 40mm across, excluding crown and pushers.



I'd prefer a UK sale, ideally face to face but I'll post it RMSD as part of the asking price - £300.
For a watch of this quality, a bargain!

 

Here is the watch for sale on the right, with its stablemate which I changed the crystal on. The left watch almost looks like it has a rehaut