@Maxppp If you have never serviced a watch before I do recommend you practice on something else first, for example a Vostok 2409. It's a stunning timepiece you have there and there's a real risk you'll damage something or lose a part which might become very difficult to replace. There's always a risk, even when you're experienced but with experience you'll learn to minimize the risks.
Best of luck!
Any way suggest the best way of removing this screw.
Do not want to drill it incase i destroy the thread.
Ain,t there some chemical i can use that will dissolve the screw but not the bridge?
I might misunderstand you, but isn't the normal procedure to first service the watch and then (and during the service) do the fault finding in case the problems remain? It's an honest question, not an opinion.
Are you aware of any other significant differences besides the mainspring that come to mind just curious.
The project, it's not something I'm actively pursuing right now just in the research phase. I probably won't try to build the skx until I can disassemble and rebuild even if it is way simpler.