tazzman: visit the web site of the Mexico Elmhurst Philatelic Society Intl. (
www.mepsi.org ). They have a book for sale on Mexico revenues. If you're not interested in the entire book, maybe the author would answer any questions you have about your particular stamp. He's one of the officers. I think there may be a catalog of revenues, but I'm not aware of a title.
If you're into Mexico stamps, you might consider joining MEPSI. I'm a member myself, since Mexico is one of my several specialty areas of interest.
Addendum: I just found this web link on another thread:
www.jbarefoot.co.uk . He's got a lot of stuff on world revenues on his site. I didn't see anything Mexico specific. But It's a big site and I didn't look at everything.