Raimey,
One other hint that was marked on the rifle barrel's belly was a block "ST". It ran parallel the length of the barrel, and was right after the post that supports the splinter forend's attachment. (sorry if there is a proper term for that I do not know)
This "ST" was not at all related to the STMG bullet proofs, but was just two charcters in a fairly large block type font. It appeard to be in a similar typeface to the "Krupp" words on the gun. The only other two letter combination on the gun was the already addressed "W.K.". The difference being that W.K. was in a stylized cursive and the ST was in a bold, capitalized block set.
I promise I will post superior pictures in early August. (travelling until then) Other than superior pictures, what can I do to move the ball forward into identifying the manufacturer, engraver and retailer's identity?
Other than more cigars and liquor placed into the IOU account, what else would you need to delve deeper into this gun's history?
