The coil was issued in rolls of 500 and not sold individually at post offices. Most of the stamps were used at hotels and other places where stamp vending machines were located. Therefore most uses were non-philatelic and probably not saved.
C37 was issued on January 15, 1948. The 5c airmail postage rate was in effect from October 1, 1946 to December 31, 1948. You might think this stamp would be easy to find properly used on cover. However, in the estimation of some collectors this is probably one of the hardest uses to find of all the airmail stamps.
