Found this in a gunboard's thread in regards to the eagle over Su4
"Su4 is not a WaA acceptance. The part was accepted by the Heereszeugamt (HZA or Army Ordnance Depot) at Spandau which was not under the administration of the WaA."
As this is a WWII mark on a formerly civilian C96 the lack of imperial stamps is not surprising.
F 135 - the right choice