I grow a pepper which I obtained in Central Mexico. Our family lived in the State of Hidalgo for about 8 1/2 years and this one was my wife's absolute favorite. It was also extremely popular there. It's grown in a region called "la Huesteca," which lays in an area encompassing parts of Hidalgo, San Luis Potosí and Veracruz.
I grow it every year, here in Oklahoma and, over the last few years the question has come up as to its species. It has never crossed with anything else in my garden. True, I have tried to give it a good distance isolation from anything c. annuum, but I'm thinking it's not a c. annum. Would anyone here have an idea?
Here's a link to a thread on this pepper, with a good many pictures. I'll post a few pictures here as well.
The Serrano, a type of C annuum, is from the mountains of northern Puebla and Hidalgo. The leaves are hairy.
In Peppers of the World, An Identification Guide by Dave DeWitt and Paul W. Bosland, there is a photo of C annuum cv 'Seraano Huasteco' which is grown primarily in Navarit, San Luis Potosi, Sinaloa and Tamaulipas.