Above is a site dedicated to Clifford Harvey, W1RF and his various companies.
I recall reading one remembrance that after one of the floods in the late fifties, Clifford gave away or sold at minimal price stock that had gotten wet, cases in particular, to the local hams.
It's possible that different innards could be in a mismatched case. Or someone may have removed the "D" mic preamp. I have two D's and they have variations in specific components and exact layout. One has holes for the VFO mounting, the other does not. It is obvious that Harvey-Wells took advantage of bargain component sources. I can't account for the tube variation.