The launcher/handgun is referred to as the EFL [Emergency Flare Launcher] and was the closest thing to a semi-automatic flare gun. The small loop at the top may be considered to be the “barrel”.
Wren you fire a flare, the next one in the five round magazine ejects the case of the cartridge that just fired.
The came in White and Red, and Green, (I still have several dozen along with one EFL), in 10 packs, four packs per box, of each colour. I do not remember if you could buy a mixed colour lot
If you can find them for sale today, prices range between $3~$10 per round.
I have heard varying reports of shelf life in sealed packs being between 5 and 20 years, with 15 years being the most agreed upon, but I have no idea why. I have fired them with a date in the mid 1980s’ with no problem.
My understanding is that the flares were still produced through the early 2000’s because there were EFLs’ in inventory with military organizations and some search and rescue groups. One story goes that the factory burned down and was never rebuilt because of the “greens” and toxic waste geounds, while another says Piepenbrock Pyrotechnik GmbH merged with Feistel Feuerwerk, but I can not seem to find valid info, maily because my German sucks, and translated pages often make no sense to me.
The H&K EFl has been used in several movies as a weapon, but never as a signaling device.
If anyone has an EFL, Numrich Arms/Gun Parts Corp. has several magazines in stock for $40 each, while they listed are on evilbay at $75 and up.
Here is the G&K EFL page from the 2018 Wescom Defence Pyrotechnic Stores Handbook: