What is this model?

Don't know what it is, but the reason for the underslung fin is to allow the tail to go up 45 degrees without having to pivot the fin as well. Dethermaliser.

... implying its free flight, or was, rather; and at this size, maybe a Nordic A-1 towline glider. It does have that 1950s maybe kind of look, but the fuselage complete with a compartment suitable for radio says it was designed for a simple radio installation, like rudder only. The low fin is advantageous for one reason at least- when you use rudder, you get positive roll coupling, not a bad thing, but easy to damage. Paul