If you will take that nipple to a local Hardware store, or machine shop, where they have gauges to measure metric threads, you should be able to learn what the thread size is on that nipple. Then, you will be in a position to order a replacement nipple, OR, should the threads in the bolster be rusted out, or ruined( cross threading is a common problem with these guns), then you can talk directly, by phone, to the folks at either Track of the Wolf, or at Brownell's, in Montezuma, Iowa, across the river from you, about the next larger size nipple you can install. Both suppliers sell the oversized nipples, as well as the Taps needed to thread the bolster larger to fit the larger nipple size. If you go on-line to TOTW's catalogue, and look up nipples, they have a page with their chart of oversized nipples you can study before you call any supplier.
Old guns DO make nice projects to refinish- both the metal, and the wood. I refinished a .22 rifle for a friend who worked in an office next to mine. He had left the gun in a damp basement, and it has tiny spots of rust all over the barrel. The gun was fairly cheap to by, and he didn't want to sink a lot of money in having the barrel reblued. So, I took the gun, to try out some techniques I had heard about. They worked perfectly on the barrel, and made the factory stock, with its dinks, and gouges, and scratches simply look terrible against that newly finished barrel. So, I stripped the stock down with Acetone, to find a rather nice, straight grained piece of Birch. It even had a burl in the butt stock. I washed the stock with some B/C cherry stain, and then rubbed off the high spots using OOOO steel wool. Then, I hand rubbed on a finish of Gunstock oil finish, in several layers, until I had a very fine finish. It made the gun look like a "million bucks" I stripped the gun down, and cleaned it thoroughly. I oiled it, and then put it back together and test fired it with new ammo. When I gave the gun back to Bob, he didn't recognize it. Only the serial number convinced him it was his gun!
But, most of all I had fun. I was able to try out some finishing techniques for both barrels, and wood. I enjoy stripping and cleaning makes of guns I have never handled before- and am relieved when they go back together without me holding on to some "extra parts!" :shocked2: :wink: )I removed some burrs, from inside the action that smoothed the action, and decreased the trigger pull to something an ordinary human could use to fire the gun without the aid of a troop of scouts. :rotf: :idunno: When the gun fired perfectly, ejecting the empty casings correctly, and reliably, I was ecstatic. I have the same feeling when I tune Mlers for others. :surrender: :grin: :v :thumbsup: :thumbsup:
So, go for it. There is about NOTHING you can do to that pistol to ruin it, considering its present state. If your work turns it into a better looking gun, and a shooter, all the more power to you. :hatsoff: