Heck I have seen a bunch of pre war M70's with original 20 LPI checkering! I guess haven't seen any ones old enough. I have seen and owned a few 1936's, 37's, and one 1938. They all had the 20 LPI. They switched to 18 LPI in 1941. There are tons of 1941 M70's; at one time almost every pre war you saw was a 1941. I can't say if I ever saw a 1941 with 20 LPI, but am fairly certain there should be some of them.
