Drew, it may be a West German proof mark. The squashed buzzard looks something like that bird,and the crown with the W may be the German choked barrel proof mark. There are issues with these guesses. The WGerman proof marks with that bird all have letters underneanth but no crowns,and the crown with the W was not used after 1939,or so my book says. If we surmise that the 75 is the date it was proved{1975} it works out.