Hello, everyone. I didn't receive any response to my recent subject
post but have found the answer myself. I was only searching USPTO
patent class 70-21 instead of including class 70-25. Under class 70-25,
Master Lock patent #3563067 of 2/16/71 for an improved permutation
padlock appears to describe the internals of the currently-marketed
Master #1500/1525. I am assuming that Master began marketing the
improved design in the early 70s.
The foregoing is provided for those like myself that are interested in
lock company history and lock evolution (especially stuff still
manufactured in the U.S. - yes, I remember Yale & Towne, Slaymaker,
Corbin, National). Sincerely,
- posted 15 years ago