The 336A, SC, and RC thru 1953 when Marlin began drilling and taping the receivers had a waffle top. The top of the receiver was machined with a wavy pattern, that I suppose reminded people of a waffle iron. Many people consider a waffle top that has never been drilled and tapped more desirable than one which has.
This post was modified to change the thru date on waffle top production to 1953 from the 1956 I had listed. I appreciate the occasional correction of more experienced members, here to learn.