You have the ½¢ Nathan Hale from the years 1925-29. It is fairly common and is usualy worth no more than a dollar in value. There are two varieties, the difference being in the number of perforations. The first variety (#551) was issued in 1922 and has perforation guage of 11 all the way around. This stamp value can be found by clicking the numbers 551-561. The second variety (#653) was issued in 1929 and has perf guage 11 at the sides and perf guage 10½ on the top and bottom. This stamp value can be found by clicking the numbers 643-657. To discern the difference see below

DETERMINING THE PERFORATIONS

To determine the difference in the perforations between #551 and #653 you will need a copy of the very common 1932 3¢ Washington (#720). A picture of which is shown below. Follow the instructions below