Some time back I mentioned having a poncirus that had more than three leaflets to the leaf. The tree has leafed out, so I thought I would show some shots of the leaves. I have found from 3 to as high as 7 leaflets on a leaf.

Ned

I've seen the odd leaf on Poncirus that wasn't trifoliate, but never a compound leaf like yours. It seems as if a second trifoliate leaf is trying to grow from the centre of the first trifoliate leaf.
There are citrus relatives that have this leaf form. Hesperethusa crenulata (or Naringi crenulata) has a compound trifoliate leaf. It is pictured in Citrus Industry, Vol 1, and various sites from a Google image search.
I expect your plant is a genetic mutation rather than any kind of hybrid. It will be interesting to see if the fruits are normal, and whether it reproduces from seed. Probably a long time to wait!

Citrange, I think you are right about the genetic mutation. There is a limb or two that has leaves that are fairly normal, even though they are not exactly like other poncirus. The tree does seem to be somewhat dwarf.

Ned