No, it wasn't that they're all battered and mostly minus their lids. Neither was it that they all have dead batteries (that's pretty standard after a week of use, to be honest). I already knew both of those things. What I actually noticed was this:
|"Retinal scan complete, Judge McGruder"|
Some of the official ones have swirls and some don't. After a brief flurry of Tweeting on that there Twitter, it became apparent that the ones with swirls are exclusively of the NTSC variety and the ones sans swirl are PAL variants. This is quite odd, as there really isn't any need to differentiate between the two flavours: both will work equally well in either a PAL or NTSC Dreamcast console or controller. It was suggested that the swirl was removed from the PAL VMUs due to the legal ramifications SOE faced due to the whole orange/blue swirl issue, but that doesn't wash as the swirls printed on VMUs are grey, not coloured.
Maybe it was just so that Sega could differentiate and identify stocks between the two regions, but it's still a nice little curio that I was totally unaware of up until now.