I believe:

M = marine
440 = cu.in.
L = left hand rotation
1-20 = engine assembly date 1/20/68 (3*23*67 block cast date)
D = 1968 model year

sideways "0" & little "c" shruggy

the Marysville, MI engine assembly plant was Chrysler Marine & also built Max Wedge & HEMI passenger car engines (similar top pad font & layout) this 440 was one of a pair, the other being right hand rotation - I'm trying to track that engine down to get a pic of the top pad.