Field post number help...

[Jason von Z.]

I just received a small collection of items, photos and letters mostly, from one soldier. Many of the letters are marked with the field post number "25936" (mid-1943). There are also a couple of letters with the field post number "40792 A" (late 1943, early 1944). Can anyone assist me in identifying the units denoted by these two field post numbers? Thank you in advance.
Jason

[Ian Jewison]

25936 - Stab III u. 7.-9. Batterie Artillerie-Regiment 291
40792 A - Stab Reserve-Panzerjäger-Abteilung 7

/Ian