As noted here, the US was not the only mail service using locks with counters. This example comes from the Phillippines:
Vintage 1950s (or earlier) brass registered Philippine Mail padlock with replacement key. On the side, the lock has a moving and working counter to indicate the number of times the lock has been opened and closed. Made in the Philippines by "Vicente Zamora". - eBayThis item sold for $88.88 (plus $8.78 in shipping)
Oddly enough, this sold for less than most US Registered mail locks sell for.