I went by the tree in north Birmingham Alabama today and was given permission to grab a few mature fruit. The smell was similar to trifoliate orange though the fruit was the size, shape, and color of a ripe orange about 2 1/2 inches diameter. Flavor was distinctly bitter with the sharp flavor of a grapefruit. Each fruit had about 10 seed. The fruit had the sticky resin typical of trifoliate orange. The tree was not covered in spines, however, the tips of the limbs were distinctly sharp. From the look of the tree, I suspect it was damaged by the 22 degree weather we had in mid November. The tree had a very heavy crop of fruit this year. Based on the combination of characteristics including cold tolerance, bitter grapefruit flavor, and tree form, I think this is most likely a citrumelo or from very similar breeding. I have about 50 seed which will be planted tomorrow. I figure the resulting seedlings have potential either for fruit or as rootstock. I am aware of the tendency of citrus to produce apomictic seedlings.