I have a .36 Black Powder revolver that needs a replacement spring and the only identification that I can find apart from, "Made in Italy" is on the bottom of the but punched into the wooden grip which appears to say.
"L. H. Co S.F.K. Laxfgeld."
Look under the loading lever and the bottom of the frame. You might also try the recoil sheild. I've seen a couple ASMs that had proof marks & date code on the recoil sheild where they couldn't be seen when the pistol was assembled. Here is a link to a webpage that will help you decode whatever markings you find. https://store.bluebookinc.com/Info/PDF/POWDER/MBPProofmarks.pdf