Although the Lab and the processes were still young, this document reveals the ability of science, and in this case the Lab, to restore obliterated serial numbers on weapons.  Much of what Appel learned with regard to scientific examinations came from the teachings of other crime lab persons outside the Bureau.  This example is on a Thompson .45 caliber machine gun.  Notice that the acid testing on just this one item took five hours!

The name at the bottom of the memorandum is "T. F. Baughman" who no doubt is "Frank" Baughman.  Baughman was one of Hoover's early associates at FBI Headquarters and Baughman is regularly seen in many 1930's photos as present at firearms training courses.  Many times in these photos, Baughman is mis-identified as a Marine Corp. instructor. 

By the way, the firm mentioned in El Paso, Texas I suspect will be Wolf and Klar which was associated with Texas gun dealer, Harold Lebman, who supplied some of the Dillinger related gangsters with their weapons.  More on Lebman is in the navigation area. 

As time goes on with this website, you will find more on Baughman, Charles Appel and the Lab in the navigation area or doing a site search.