It is not a bottle, but cylinder.
Tanks are those big things that are bolted to RV frame and have the big fill up valves that can load 30 gallons in just couple of minutes.
Also those you see in front of the house are tanks as well.
Tanks don't require any certification and as long as those 50 years old look good, the service will fill them.
Anything that can and needs to be removed for fill is a cylinder.
Cylinders need certifications every few years and have self-closing valve that prevents overfilling.
I think forklift cylinders fall between.