Warning!

Have you seen these cylinders?

Sidewall stamping is NOT PERMITTED in 3A, 3AA, and 3AL!! These were marked this way by the manufacturer, and they must be condemned. DO NOT requalify cylinders with stamping on the sidewall.

Unless authorized by the specification (3E and some 4B, 4BA), this is not allowed by the manufacturer (or the retester).

Here are the DOT CFR and TC B339 sections for marking of cylinders by the manufacturer:

DOT 49 CFR §178.35(f)(4) & (6):

TC B339 §4.17: