Hi Laurentius!
Now we have a problem...
I also see a 5 with a grenade. Feldartillerie.
BUT:
FAR5 was a silesian unit. Fifth Army Corps. In peace time they had yellow shoulder-straps, so on this 07/10 tunic should be seen: grey shoulder-straps with yellow pipings.
Or should it be officer boards? But then too, the pipings might be yellow.
And Feldartillerie hat swedish cuffs.
Swedish cuffs: Two buttons horinzotal
Brandenburg cuffs: Three buttons vertical.
What about the red patch at the collar? Upon a 07/10 tunic those red patches didn´t exist. They were worn upon a Litewka. Do you have close-up please?
Can you also please show the sword?
I assume, the painter used "artistic license"... There is something wrong...
Here is a Lieutenant of FAR600 with Litewka and black collar patches: