Oxygen & Acetylene setup advice

Yeh, we used to have a lot of the collared tanks around here, too. I have a smaller "B" tank for an air/ acet torch I use for heating bolts on outboard, and it needs a "key" A "key" was part of my life in my HVAC years. It was on a cable permanently tied to the torch set. I've hauled that thing up uncountable ladders over the years.