Randy Emerick, a very good friend of mine and an aficionado of saxophone (as a professional musician, instrument repair tech, and sax collector extraordinaire) send me these two blasts from the past. He knows I have played the Conn-o-sax and actually own an F Mezzo soprano sax. I have often said they are the best saxophones I have ever played. He sez,
“About 25 years ago I went to Ball State University in Muncie, Indiana to do a talk on saxophone history for George Wolfe, the sax professor there. At the time Ball State was the home of the Cecil Leeson sax collection before it was moved to the Musical instrument museum. I photocopied some ads from Conn’s periodical, “Musical Truth” including the original announcements of the F-Mezzo soprano.”
It is interesting to me how they marketed the mezzo. I can tell you one of these horns in top condition fetch better prices than most vintage and used modern saxes.
The Bis Key Chronicles 
1/29/2012: Just yesterday, Aquilasax of New Zealand, known for its re-issues of modern C-Melody and C-Soprano saxophones, in response to customer inquiries, announced that they would consider “re-issuing” the F-Mezzo Soprano saxophone if interest is high enough. They have added a page to their online store, asking that serious interested parties register their interest by signing up on a waiting list. “If we get enough interest, we will consider proceeding with development and will require a deposit to begin production. No obligation to register.” The cost of a new F-Mez horn (including case, mpc, & accessories) is listed as $2950, plus $65 in shipping, which is less than half the price of a restored F-Mez that as of this writing is listed on Ebay.
https://aquilasax.3dcartstores.com/F-Mezzo-saxophone_p_414.html
Could the internet bring the F-Mez back to life? I for one surely hope so.