Hi Jon, Welcome to the forum! If it helps, here are the well markings on 1917 Navy # 5302.
I maintain a data base of all known Imperial Navy Lugers, about 1,500 guns, and I'd like to add yours to the list. If you send me an email with your guns full serial number, I'll send you the link to the list.
Regards, Norm
normrab@comcast.net