Request for Help ID'ing Luger

[bmarshalladams]

My father-in-law returned from the war with a 9mm luger. I am not a collector and my knowledge is limited to what I have learned in a short time from postings on this excellent forum, which leads me to conclude this is a Navy Luger. I can advise that it;

Has a 6 inch barrel
DWM script on togglebolt
Rear sight stamped with 100 and 300 opposite each other
Grip frame stamped WW and 2798
Frame stamped 5216 at six O'clock under barrel
Rear if toggle '16'
Left side of frame behind takedown lever '91'..lever has tiny
marking and number 18
Frame has three proof markings; crown, then two 'M's
with crown on top
Holster/stock lug on rear grip of frame
No color case hardining on trigger or elsewhere

Not sure why so many mis-matching serial numbers. Is this a fairly common variety Luger, or is there anything unusual or special about it?

Thanks in advance for any comments observations.

Marshall