30 CFR § 23.12 - Wording, purpose, and use of approval plate.
(a) Approval plate.
(b) Purpose. The approval plate is a label that identifies the device so that anyone can tell at a glance whether or not it is of the permissible type. By the plate, the manufacturer can point out that his device complies with MSHA's requirements and that it has been approved for use in gassy or dusty mines.
(c) Use. Permission to place MSHA's approval plate on his device obligates the manufacturer to maintain the quality of his product and to see that each device is constructed according to the drawings that have been accepted by MSHA and are in MSHA's files. Devices exhibiting changes in design that have not been authorized are not permissible and must not bear MSHA's approval plate.