Reworked 1917 Erfurt
 

I recently came across a 1917 Erfurt which appears to be a nazi era police rework. The sear bar is stamped HZaJt18. The clip serial number matches the gun and is a Haenel-Scmiesser type 2 with a small number 1 on the top of the clip base and an eagle over circle (no swaz) on the bottom of the base. The odd thing is that the grips are brown plastic like a Kreighoff. I did not remove them. Do these grips sound correct for a rework?
Seller is asking $1200.

Bought this piece for $900. Numbers matching inside and out, nice bore and bluing. Straw parts. Imperial proofs and HZa depot mark (Ingolstad, I believe). Brown Krieghoff type grips. Police type 2 magazine matches gun (1 mag only). No sear safety.
Weimar rework?
Came from a WW2 vet who said he traded 4 cartons of cigarettes for it at the end of the war.