Mini "peanut" Yale on old mail slot

[Peter Martin]

My office building was built around 1920s. The original mail deposit slots and tubes are now disused and welded shut, but the small Yale pin tumblers caught my eye.
Kind of a neat piece of history.
As a side note, the Dillinger gang robbed this bank building in the 30s, so its preserved as a historic site.
The locks and mail slot drop was probably never officially "US Mail", but I wonder if Yale sold these commercially for modern buildings?
It looks so corroded I can't even tell the keyway.
Pete
Sioux Falls, SD