The prefix is C and it's on all three places; butt, barrel, and cylinder.

Thanks for the reply!

old jim

EDIT::: oops, i guess the C means late 1940's,,, ? my face is red... found on other threads enough to date it to 1947 or 48.... half moon front sihgt, four line "Made in USA" & "Marcus Registradas", same hammer as newer marked model 10's.

Great forum guys and THANK YOU for your indulgence of newbies.