Small bottles will not fit, I just checked. They are too long.
That's a shame, I thought I might have discovered something potentially useful.
That is a late model Vendo 56 in the picture.
Ah, a 56. One less shelf, etc. than the 63?
Bottle openers were standard on all early machines and the only real change to the later 56 was an interchangable can stack. There was really not enough reason to redesign the coin door just to eliminate the bottle opener.
So they left the coin door the same. As the opener itself serves no apparent purpose for the machine, did Vendo install it just for the looks, or would that have been added later?
You mentioned the later machines have an interchangeable can stack. Does that mean those machines no longer required the modifications detailed at the start of this thread to be fitted with a can stack?