Hidden Info, Secret Data, Easter Egg?

Hi,
I'm currently working on a series of DVDs that are tending to have multiple versions of each; fixes, minor changes, added features etc. They're consistently being updated and re-distributed.

These discs are being replicated and in the interest of keeping track of what's what, I'd like to add a version number to the discs... something that wouldn't be apparent or available on any of the main menus or programs- but something that's also really easy to access quickly in case any questions arise about that disc.

It wouldn't be a problem for an over-zellous user to come across this- but it shouldn't ever happen by accident. Of course there's plenty of ways to hide an easter egg in a menu- but I just was wondering if anyone knew of any especially clever or creative little tricks - some way of hiding something as small and simple as a version number?

Why not simply put it in the VOlume Creation field, adding it on to the end of the date stamp in there? Or better yet, each time you make a build keep a spreadsheet and list the time and date against the version number in that.

If you open a replicated DVD in MyDVDEdit or DVDAfterEdit you can look for the volume creation details and work out from that which version it is.

It would have to be a pretty determined end user to look in such a place.