Not especially unusual.
I have seen them with the "property" line removed, as well as the whole serial number removed.
Some GI stole it, and at the time thought they would get in trouble if found with those words still intact.
Of course legally, the "property of" line meant nothing.
But removing the serial number on any firearm was strictly against the law following the 1934 National Firearms Act.
Anyway, a few years after the war ended the market was flooded with surplus 1911's at about $17.50 a pop to NRA members from the DCM.
So all they accomplished was to ruin a good gun.
rc