I count 5 different schematic not including HF1 or minima (2014).
The design was evolutionary and the first production boards are V3, then V4 now V5.
V3 had the TDa2822 (major item), first production.
V4 had discrete transistors for audio and pads added to allow the RD16HHF, they shipped with IRF510s.
V5 changes the 12mhz if to 11.059, uses the LM386 for audio along with relay changes.
Those are the notable changes there are others but that the three major boards.
Prior to V3 it was one off builds be various people.