I have had some success in my quest. I was able to find two patents from Hungary under the name Szladeky for this lock. While it may have been used on postal sacks it appears it was patented for use on money sacks for “SZLADEKY SUBSYSTEM PAYMENT BANK” in Budapest. I am attaching the patent info as well as my best effort at translating each of them.
1
Újítás zsákzárakon
Type of application PATENT
Reference number of the application 56047
Registration number 56047
Application date 1911.07.11
Rightholder Szladeky Alajos ; Budapest (HU)
2
Zsákzár
Type of application PATENT
Reference number of the application S-11826
Registration number 93688
Application date 1926.06.04
Rightholder Szladeky Alajos ; Budapest (HU)
While finding these patents has brought me a long way I am still open to any other information one might have on these unusual locks.
Thanks!