this looks like a paper shot shell. brown/lt tan w/cardboard top wad brass base, 3 red stripes around shell.in desending order it reads: TR. /// flameing bomb / SIGNAL, AIRCRAFT,TRACER /// DOUBLE STAR M57 /// LOT UM-7-7 /// OCTOBER1943…primer is 1.65, copper, inside a 2.70 cup(?) marked w.r.a.co. @ 12 // newno4 @ 6. its 3.855 to the roll crimp from base, 1.521 paper case, 1.550 brass base , rim 1.685 . what exactly is it an its use ?
As Pete says, it’s a signalling flare to let other aircraft or ground controllers know what their situation is; there was a complete list of what each colour and/or sequence meant, but the idea was that one or more of a particular colour or another meant such things as “wounded aboard, we need landing priority”, “aircraft in danger of fire aboard”, “aircraft out of fuel”, etc. Since the radios they had weren’t always reliable, and were quite often shot to bits anyway, they needed some way of relaying these messages.