Peter, that chook (chicken...) looking thing is a bona fide US Inspector's stamp, believe it or not. The 'flaming bomb' (grenade) is the US equivalent of the 'Broad Arrow' in the Commonwealth system. The chook is a stylised bald eagle with the factory inspector's number.
The 30 is the year I'm told....... and similar to our reissue dates, I've seen dates from 26 -30