A teeny tiny Sowar Prima

This watch I bought for my wife. I've not put any scale in the pictures so it's hard to tell but it is less that half of any of my other watches in diameter (~19mm, 8 3/4" apparently). The second hand is so small it's hard to make it out with the naked eye.

I've done no more than take the back off this and haven't needed to. I don't know if it's been serviced recently but it's keeping good time and running fine (there is a note that says it had it's stem replaced in 1999). The strap even looks original (though definitely needs replacing). I haven't identified the movement yet but I suspect it's some kind of late 30s/40s FHF.

The green between 10 and 12 o'clock in the first picture is not an illusion. It's copper corrosion in the paint. Not a lot I can do about it unfortunately. You can see a bit more on the case in the second pic. I suspect it's got wet at some point.

It is of the same style as the "CSI" Sowars, but has not been stamped as such. It does have "Brit Pat. 386 505" inside the caseback, which is a bit different and according to the patent office was registered in May 1932 by Taubert et Fils: "Improvements in Fluid Tight watches". Not completely fluid tight judging by the verdigris...

Note the slightly different numbers stamped on the different sides of the caseback.