There are quite a few options here. The Pro V1 was first introduced on Tour in 2000. The packaging is different. Side stamps/lines. Is there a particular design/year, that you're looking for; ex: 2003 compared to 2013, etc.?

I think this is exactly what your looking for. http://blog.lostgolfballs.com/pro-v1-vs-pro-v1x-the-truth-revealed

While this is an interesting discussion, I think an intersting ancillary point is that in this forum people have discussed the longevity of the balls.  I believe in summary, if Titleist balls are stored at reasonable room temperatures they have a long shelf life and performance is not impacted very much at all.  Thus, as long as you purchase the current model since they have a two year shelf life you should not have any issues.  I am not certain if this applies to competitors however I am happy to continue to play and purchase balls from golf course pro shop knowing they will always be fresh.

Just a thought, Chris