Got this case as a gift after celebration in Salzburg (Austria) this week. It was used to fire 17th-century-looking cannon during the parade.
Case is made of aluminum, COAL 79 mm, rim dia 30.4 mm, external diameter near the mouth (just before the crimp) is 26.4mm.
I suppose it is based on some sort of 26mm flare gun round, but any info on manufacturer and actual load (sort of flash-bang, possibly black-powder?) is appreciated.