Hi folks, I have a Hamilton 992 Elinvar that has slippage when winding so I'm guessing that I will need to replace the mainspring but I haven't taken it apart yet.

What I am wondering is, are mainsprings interchangeable between 992 models?

I have to go looking for the replacement mainspring and need to know if I have to be specific about what I need for this particular movement or if any 992 mainspring will fit.

Thanks

Ralph,
The 1951 Hamilton Watch Materials catalog lists the #534 strength 16.5 refill #210 mainspring for the 992 and 992E. The new part # is 718047. It's best to measure the thickness of the spring you're replacing to see if it's .165mm strength and if not replace it with one of the same strength or close to the old one if possible. The #534 mainsprings are interchangeable but should be the proper strength for the movement, balance, and hairspring combination. The #534B mainsprings are not interchangeable with the #534 mainsprings.
Hope that helps,
RR

Hamilton Mainspring Part Numbers

Thanks Richard, that info gets me going in the right direction.
Ralph