My grandfather gave me a Hohner Chromonica back in the 80's and I All Hohner harmonicas had 4-digit date stamps on the reedplates from. Here's what we know: We can't usually get an exact date of the harmonica's manufacture. There are too many factors involved, and Hohner has never kept.
The physical dimensions are identical to the standard Marine Band, as well as the reeds. Here, Hohner sanded the sharp edges of the mouthpiece and sealed the entire perimeter of the comb with a finish that will prevent swelling. Tuning is identical to the standard Marine Band.