My Family Luger, please help identify

[thor179]

I am a little confused as how to ask a question on this site. My Grandfather was a merchant marine (US) in the 1920's. The past is a bit shaky as some of the Family was from Austria prior to WW1. His Luger is now in the hands of my parents with the intent to hand it down to me. Funny thing is he Spoke German and was fluent in it but had No accent when he spoke English having spent most of his life (if not all) in England and the US. He actually spent 1 year in prison in London as a suspect for the Lusitania sinking! Anyway the Luger has the DWM marking as well as a small crown with a N under it on the barrel with a 747 under that with a mark that looks like a 7 jammed next to a backwards S. it is a 9mm, the piece has the original wooden tabbed clip and seems in really great shape. My dad fired it for a clip or 2 and it is in perfect firing condition. Any help getting the age of it would be appreciated. I am trying to get and estimate of value for insurance purposes as i am not planning on selling it.