[GA_Collector]

I have an RC BNZ 41 (d block).

Instead of having 4 WaA623 stamps on the right hand side of the receiver (as mentioned in Law's book) it has 3 WaA623 stamps and 1 WaA77 stamp.

At point, did they start to change the WaA markings?

 

[malaki]

The Wa77 simply denotes that your receiver was made at Radom in Poland.

Steyr made receivers (large font): WaA623 x 4
Radom receivers (small font): WaA623 x 3 & Wa77 x 1