What's the (H) stamp, one or two places I looked it says a test firing proof was an E HK left on the slide. Is it a different test firing proof?
Is there a definitive way to date it, narrow down the date, as I understand, these had a pretty long production run?
Or is between 1942 and 1944 as close as one can get?
GM the (H) stamp means the pistol was accepted was accepted by the Belgian Military stamp used from 1921 -1940. the E is the FN inspectors stamp (August Jamart) 1924-1959 per Anthony Vanderlinden's book. It is also important to know if these letters are inside a square or a circle. Don't know about the HK stamp.
The Germans captured the plant in May of 1940. The pistol was probably taken of a Belgian officer after capture. Anthony is on Jan Still's Lugar forum a lot
http://luger.gunboards.com/forum.php. If you take it there he may be able to tell you more. After all he wrote the book on the FN Browning Pistols.