I'm starting to catch on. Went to the cabin - rotated cylinder +/- 10 degrees and I see that what I thought were plugs are in fact holes in the inside front plate that are backed by a plate that rotates with the cylinder. From your comments I understand that if I had the key I could rotate the cylinder to a location where there would be holes in the rotating plate that would line up with the holes in the front plate - at which time I could use a phillips head screw driver to remove screws that hold in the lock.?!
The lock is probably 75 years old and I don't mind buying a new one.
This being the case are my reasonable options (1) hire a locksmith to go up there and pick the lock. Then I could remove & replace old lock or he could maybe make me a key? Assumes that blanks for the HARLOC are still around?
(2) take a drill and drill thru the pins - then put in a screw driver and rotate the cylinder to where I can remove the screws.
Am I getting it right?