Need help with Unit Mark?

[barr44]

Folks,
S.n. on this 1917/1920 DWM is 7387a and I am attempting to add some image files.
Hope this info helps. I am curious as to what this unit is about, is this a school? Also if this pistol was attached to a police unit would it have been modified with the additional safeties? This gun has no sear safety. Also the barrel has been replaced but numbered to the gun, and seems to retain an imperial proof. Would this be part of the rework program?
As near as I can determine it is all matching, even though the barrel has been replaced. Again any information forth coming is appreciated.
Thanks, barr