I think both are 8620. Jim and Barbie have posted the alloys used in their locks, but I haven't been able to find them using the Forum's search function. Perhaps you will have better luck.[/quoteWhen I was making locks,8620 was for plates,hammers and top jaws and 52-100 for frizzens (hopefully)This was back when most of my parts came from Jerry Devaudreuil in Wooster Ohio and doing business as International Arms.It worked well and I am assuming the foundry DID honor the request.Log Cabin now owns all his moulds and maybe left over parts.This has nothing to do with Jam and Barbie Chambers parts but may give an idea as to the variety of materials that can be used,Bob Roller