Big problem with the AMA. When they moved from the DC area. my understanding is many of the records got lost, tossed. or eating by a pack of dogs, etc... this may not be true, but don't hold your breath. That number is low enough to have been issued in the late 50's... D>K
There is a P40 hanging in post VFW 799 I'm trying to figure out who built it. AMA 18723
My AMA is 19775, was issued sometime early 1960's. Number you are interested in is approx only 1000 earlier and someone sys its from 1940's. ? Doesn't make sense
Best pic I can do