Rare and under appreciated watches, calibre 1300 and the first swiss quartz production watch, the same movement used in the original IWC Da vinici, the first Rolex Oysterquartz, Patek Quartz, Rado Quartz, the first Jaeger master quartz etc etc.
Useful article here:
https://en.wikipedia.org/wiki/Omega_Electroquartz
The original screw all go that green over age, its a tell tale sign of an unmolested watch. Colin is right, no where near the value of a stardust but a good NOS example is £1000 - £1500 now, a good non serviced/ non NOS example up to £1000. Plenty of people such as keithT on TZ who can service them inexpensively so long as they are working
If it is running fast it is simply double stepping, it just needs a service, I have spare circuits for these if thats the issue so snag it if you can.
Hope this helps
Cheers Tom