1917 Erfurt 7.65 - Need Help

[whr_iii]

New user, apologize if I am posting this incorrectly but sure would appreciate any help. Inherited from my late father his prized 1917 Erfurt Luger, SN 8714. He was never able to fully identify having consulted several resources to include books from Datig and Reese. Didn't have the internet so thought I would put it to use to hopefully solve his quest. Particulars are 1917 production year, Erfurt stamp by toggle, smooth vs checkered grips in 7.65mm, Yes, 7.65. Barrel is 4", all SNs are matched except magazines. Holster is not original (for this pistol) as was produced in 1940. Everything says this should not be 7.65 rather 9mm. Can anyone help? Much thanks.

Uploaded some photos, have several others if needed. Also have in very high res (3MB+) if desired.