One of the many versions of this watch you can get on Ali. It's either NOS or reissue of the 70s watch with Tongji, Chinese standard movement. The strap is 19mm which is a pain, I'll have to figure out a strap that fits because my current 18mm wobbles.
Anyway, this is my second hand-winding watch and the knob is kinda hard to twist so I worry about snapping the spring/bar. Especially if it actually happens to be the 50y/o movement. I already did that with the first manual watch I had.. So I'd like to ask for advice. Really don't wanna break it because it looks very nice and is pleasant to wear with the low profile (much thinner than my automatics)
I got it on a lucky discount for 406czk (~$17USD) Cheers
edit: I found an interesting article in chinese that mentions this watch belonging to author's grandfather. Same design in their photos, and the back stamped with 7120937 just the same.
And the movement in this watch should be the Standard Chinese Movement - SS7 variant. Hope I can get a watchmaker to take a look at it, and see what marking is inside to date it.
19 jewels, ticking at 21600 and should take 20 turns to wind.
edit2: i managed to open the back carefully without scratching it, and there is no markings on the inside, as there should be with vintage movements. so this is a modern release. there is no grime or anything, so i assume the winding strength is some sort of o-ring that waterproofs the watch. iirc, the original spec of the tongji watch was to survive 1 minute under 1 meter of water.
and wile it was open, i tweaked the rate, and got it from 54s/d to 5s/d.
pic inside the case - imgur
If it's oils, then you have two options:
The latter you can learn to do yourself, but be prepared to break/lose some components on the first few tries.
Good luck!