The bent tube with the brass fitting at the tip (above the barrel)...I'm pretty sure the bent tube is from a grease gun and the tip might be a grease gun tip that has been plated.
I searched for the bottle for a while and eventually found Nitrous oxide bottles I don't know if it's them or not but it's the closest thing I've found and they sure do look like the bottle.
To me the main tank looks like a small aluminium 1,5 liter air cylinder by Luxfer that's sometimes used by divers for drysuit inflation (with air or argon).
The valve I don't know, it's not a type that is used for scuba diving as far as I know.
The small container looks like an air pressure container made by Festo. These are usually used in pneumatics.
Might be from another company but the 0.4l version from Festo seems to look spot-on.