These are 22 inches long, about the width of a coke can and are sealed both ends - can anyone enlighten me as to what the heck they are?
Mystery tube? It must be the Northern Line. Q: "When does the next Mill Hill arrive?" A: "It's a mystery."
My guess is it’s the internal cylinder in an early fire extinguisher. From here http://www.cherwellfiresafety.co.uk/fireextinguisherhistory.php#.VHeXI75V7Z4 An early dry chemical extinguisher, the first ones had copper cylinders, this one is steel. In 1928, DuGas (later bought by ANSUL) came out with a cartridge-operated dry chemical extinguisher, which used sodium bicarbonate specially treated with chemicals to render it free-flowing and moisture-resistant. It consisted of a copper cylinder with an internal CO2 cartridge. The operator turned a wheel valve on top to puncture the cartridge and squeezed a lever on the valve at the end of the hose to discharge the chemical.
