Soooo. My dealer took my amp module in for repair, and offered me a loaner amp module...
But they also had fresh AMP12 stock in!
Sooooooooo. I bought an AMP12. LOL. Demo at the dealer (apparently one night of burn in) suggested that there was more detail. I'm listening back at home now (new set, 0 burn-in), and I think it's more detailed than my amp12mk1, there's a hint too that it's a more "spacious" sound.
The leather case feels better constructed than the blue case, but the material is still fairly low grade leather. I'm glad it's black though! Will still be in the market for a replacement if there's a Dignis case.
@Kiats (and generally all, FYI), there are some AMP12s which have the faint lettering yours has (the demo one I listened to looked like that but I didn't think to photograph then next to each other), but there are others with quite easy to see lettering.