M880 gun ring?

[michigandon]

Have any of you guys ever seen an M880 with a gun mount on the roof? I am contemplating the acquisition of one which the seller claims to have a genuine USGI field modification with a roof cutout and a canvas cover to go over it when not in use. Supposedly it was an MP truck and the canvas cover has an NSN number on it.

I could find nothing on Google to neither confirm nor refute his claim.

 

[NDT]

I have never seen such a thing. The M715 had one.

 

[w200/m880]

gun ring

anythings possible,see this pic