Faint block stamp

[All American Racer]

66, I use an optical micrometer at work. If you can get your hands on one you'll be amazed at what a metal surface looks like magnified many times. All it is (in a nutshell) is a lighted hand-held microscope that rests right on the surface you need to measure. In this case you won't be measuring, however, the magnification will show your #'s.