Replacement keys for antique United States Postal Service and National Park Service rotary counter locks.  Models made from original keys.  Scans of original keys provided for reference.

There are newer models of the USPS rotary counter lock.  You can identify them because the indicator window is flush with the housing, and they do not have the additional pin on the side of the shackle.  I do not know if these use the same key as the older model.

To open the padlock without breaking the plastic key, recommend inserting key into lock keyway, then press/rotate the lock shackle to open.  Do not rotate or twist the key by the bow were it could snap. See video for reference: