You may want to check with Mark's Born Again Bird Guns - he usually has a couple Merkels in his inventory and he posts here.
http://www.mbabllc.com/page/page/7927803.htm

A couple years ago I had a hammer spring break (a crack, not all the way through) on my Simson (vintage 1979). I contacted Merkel USA to see whether their parts would work in my gun. They advised their springs would work and I got one, had a local smith replace it. I think the spring cost like $50.

I think it's safe to assume Merkel spare parts will fit your gun, at least until proven otherwise.

Last edited by Dave in Maine; 10/24/15 06:10 PM.
fiery, dependable, occasionally transcendent