Citrus x Floridiana. Oh, a hybrid. And eh.. what? It's not a lemon! It's a "Limequat"!
What the hell is a limequat?
Wikipedia Limequat says: "The limequat (Citrus × floridana) is a citrus hybrid that is the result of a cross between the Key lime and the kumquat, hybridized by Walter Tennyson Swingle in 1909"
Engineer Jansen knows the Key lime from the very nice pie, so if this is like that all is good. Although someone named “Swingle” does not immediately sound really trustworthy (sorry).
Oh, and "Limequats are used in cocktails and fruit salads, and can be candied whole. They can be cooked if the seeds are removed, as they impart a bitter taste, and they can also be made into conserves.". Good too, but skip the fruit salads, too healthy!
"It is a small tree that grows into a contained bushy form. The leaves are characteristically citrus-like. The limequat produces an abundance of fruit even at a young age. The fruit is small, oval, greenish-yellow and contains seeds or pips. It has a sweet-tasting skin and a bitter-sweet pulp with a flavor similar to limes. The fruit can be eaten whole or the juice and rind can be used to flavor drinks and dishes. It has considerable amounts of vitamin C and is highly acidic."
So far this is not a small citrus, it is nice and tall.