Zone 2F of that drawing only shows -2,-3,-4 and -5...but that drawing's last revision was in 2010...so -6 and -7 may be valid number, but I could not find a real explanation of what they meant either. That drawing also shows that Lotus only bought -2 and -3… Do your calipers have Lotus P/N A120J4001F on them? Or do they have A128J4001F as a P/N on them? If they have A120J4001F, then my guess is that there is some minor change like paint or finish difference between the -2 and -3 and the -6 and -7. If neither Lotus number is there, then I think you’ve got an aftermarket caliper.