The photos are not quite detailed or close enough for me but I will say this. I have now seen two Czech Mausers that I am sure were "Brno" sporters without any of the normal Brno marks. The one in my possession has one tiny "circled z" on the bottom of the receiver. The other I wasn't able examine that closely but it was Czech proofed, as is mine. Both rifles have/had many parts (besides the usual mauser interchangeability) that are distinctly "Brno"

All this says to me is that the Arsenal that made the "Brno" trademarked rifles also made others from time to time. Maybe individual workmen took projects home, who would know.