Chris Green wrote:I believe the instrument is intended to be a french horn (or trompa francesa in Portuguese). It is however unusual in that the mouthpiece end is inside rather than outside the circular tube. I can find no image on Google of a horn that matches it. Perhaps it is unique to Portugal, or perhaps the heraldic artist had no access to the real thing (but then why would the Portuguese Air Force accept the design?).
It looks more like a sousaphone to me. http://en.wikipedia.org/wiki/Sousaphone