Greg's right on the little mystery of the Marrion "MM" model. I think it came out in the wartime years, when Rawlings was very limited to producing retail gloves like the other
sporting goods manufacturers who were turning out military gloves and items and were prohibited. The MMs I remember seem to be the wartime service models : U. S. Army, U.S. Navy and maybe some that came out retail in 1946 and '47 like OKdoke says. The G600 Marion was a very popular kids glove in the latter '40s. Mantle got one as a kid.
Happy New Year to Every One!
