Very flares were Britishsignal flares used during World War I and World War II (and still used today). They were produced in three color variants; green, red and "whitestar". The flares come in 2 sizes, 26.5mm and 38mm; both sizes have a "burn time" of ~5sec.
A typical WWII-era box of flares contained 10 shellss (fired from a very flare pistol) and the value of a period box (with flares) is currently (2003) ~$8080.
"Rockets and Very flares trailing their long red tails were fired at the brightening wisp of yellow, shining palely now on the obsidian seas silently rolling over fleets of sunken ships and armies of drowned men and untold stores of treasure lost forever." (Leckie - p.3)