Thanks to both of you for responding.
Sapote, you may be right to question the "ataulfos", although in past years they were completely yellow. This has been the first year they have had a red blush. That accompanied a spectacular taste this year. Two other strikes against them as ataulfos are that they seem to have more fibers than I would expect from their description and I am now told that the stone is not as flat as an ataulfo would have.
Just for information, the ataulfo is widely described as a Mexican mango developed by Ataulfo Morales Gordillo and registered with the Mexican Institute of Industrial Property. It seems very closely related to the Indonesian manilla.
This is an enthusiastic description and pretty much describes the taste of the ones I have.
I suspect I won't get much further with pinning down the variety and they could be quite old since I live near one of the first New World Spanish missions in an area that doesn't have a recent history of mango cultivation other than the missions.
Thanks
JF for the pointer to the mamey too. This seems to reinforce my suspicion that what I thought were ataulfo mangos may be an older variety too. Do you have any references to the mameys? I hunted on the web but barely found confirmation that such a variety exists. Your information helped me greatly and I found a 1915 paper from the American Pomological Society describing the mamey. Also discovered it, and other fruits of Caney de Oriente were worth singing about. My mameys are the least tasty and most fibrous of the varieties I have here. Even so, they are well worth eating.