I ask this is because i want to know how many certified 300bs used on cover there are. I think just my pair. This one is rarer then mine a left cut line still on it would put it in only two positions of the 180 positions. Used on cover would be exstreamly rare to find. Left lines are the rarest of them all. I measured the stamp it is the same size as my certified 300b pair on cover,and a 1909 date will be well worth sending in for a certificate.