There is a book "Catalog of the Revenue Stamps of Mexico" that will probably list it. The APRL (American Philatelic Research Library) has it and if you are an APS member you can borrow the book. For one stamp that is probably overkill.
Actually, the Stevens book has not been published since the 1970s. What you want is the newly released (2011) "Mexico's Revenue Stamps" published by MEPSI. It updates the Stevens work with current pricing and is full color and hardbound.
It is available from Eric Jackson for $65 shipped.
The stamp in question is catalog number DO310, cataloging 20 cents.