A postage meter is a device that produces an imprint that is a substitute for both the postmark and postage stamp.
The HA code identifies the meter manufacturer: Hasler
The letter O before a meter classification indicates that meter text includes “U.S. OFFICIAL MAIL.”
The USCS Postmark Catalog lists only one ship, USS Hunley (AS-31), as having used the Meter OHA1 postmark.