Must be the serial number. I'm sure that there are quite a few tapes that are sold as part of whole collector's package and a number of them went to folks who are friends/associates of the band/producer. Still, it would seem that enough have been sold to make other bands/producers take some notice.
I agree that some of the sound is probably digitally manipulated at some stage. For anyone who's seen much live music lately, it's rare these days to not see at least a few computer monitors sprinkled around a stage. Of course that's nothing new for stuff like keyboards but I would guess that live vocals with stuff like Exciters is pretty common.
I asked some questions on their Facebook page so we'll see what they say.