This part of IEC 60534 specifies mandatory and supplementary markings of control valves.
Some mandatory markings may be inappropriate
for some valves of special design, and some
supplementary markings may be appropriate only to specific types of control valves. It is recommended that the marking of all valves conform to this standard whenever possible unless otherwise agreed between the manufacturer and purchaser.
Mandatory markings should be located in such a way that markings remain permanent.
Mandatory markings shall be integral with the valve body or on a marking plate (distinct from an identification plate) securely fixed to the body.
The location of supplementary markings is also specified. Usually, these are on an identification plate.