Hello flyboy and welcome to the forum. Your Early Wartime Army HSc was produced in January 1941, one month after HSc production began in December 1940 with serial number 700001.
The Eagle/655 you mentioned is the Army Acceptance Mark. There is also a small Eagle on the left side Frame tang next to the Hammer known as an Army Test Proof or ATP. The Eagle/N is a German State Test Firing Proofmark that signifies the pistol has met safety standards.
If the Magazines are correct vintage they should have the Mauser Trademark stamped in the Floorplate. You did not mention markings on the Holster so that is an open question. I certainly hope the pistol is not stored in the Holster since it would be detrimental to its finish.
Finally, if the "Capture Paper" can be located it will add approximately $100 to the value of this HSc. This was issued by your Brother-In-Law's unit authorizing him to bring the pistol home. It will provide historical provenance that can be used to trace his unit's battle history.
Anything else, please let me know.