Just to wind up my story on this thread, I had a chance to sit down and talk with the owner this afternoon. He confirmed my hypothesis that the gun was indeed a WW-2 bring-back that been gifted to his great Grandfather. He didn't have any papers.
He also confirmed that he wanted to cash it in and I suggested he take it from here on any sale. I gave him the benefit of my research and of all the great information I gleaned from you on the forum. One gentleman from the ShotgunWorld site johnr recommended is particularly interested and has contacted me. I handed him off to the owner and wish him well.
Thank you all for an education on a subject I really knew nothing about...Geo
P.S.: If anyone else would like to contact the owner directly, just PM me for his name and email.
