I believe the Wz.28 was made in period 1929-39 fluently with some changes post 1933, as no flashguard was used by some collectors was it designated as Wz.29. Post this 1933 is in Poland changed the designation to Wz.27 for non ringed bayonets (Wz22.24.25.27) and Wz.29 for bayonets with barell ring (Wz28,29) The 1939 was different designated and so exist by some collectors called a mobilisation version, anyway its too mentioned in polish literature by Tomas Pietrzak too, who spoke about 4 types of marking.
I assume the german changes was done in field or by divisional works. On WaA77 proofed bayonets is more real the end production was done by Radom as E/77 was assigned to this plant.Majority of them doesnt have a polish rifle serial number on crossguard. b.r.Andy