I've always recognised at least 6 marks of ED Racer (counting the Super Racer as the Mk6)
Mk1-red fins, spinner, prop driver, no web between front and rear ball race housings, chromated (black) crankcase
Mk2- " " " , strengthening webs between front and rear race housings, black crankcase
Mk3 " " " , solid parallel front housing, black crankcase
Mk4 " " " " " " " , aluminium crankcase (some polished, some dull)
Mk5 plain fins, spool type prop driver, sleeve prop nut, aluminium case
Mk 6 plain fins, unfinned head, tapered front housing smaller dia front bearing, grubscrew type prop driver, black plastic backplate and disc assembly in std, R/C and 90 degree downdraft carb versions

....and that doesn't include the factory reed valve versions with green anodised parts rather than red, or some of the transitional variants around the mid 60's -Mk4/5? some of which had no exhaust stacks but a Webra silencer [no doubt as a result of the association ca 1964 with Webra that resulted in the Webra made ED Hawk 1.5cc]

ffkiwi