One of our customers has a special name plate made up that says "Pipe" with the design conditions on it.
Typical design info on their plate is:
MAWP
Design Temp.
Corr. Allo.
Pipe Spec.
If there is not a pipe spec, they usually have some material data on the plate.
We have also performed calculations on Code stamped pots to "restamp" them as pipe. This is usually done to increase inspection cycle lengths. This is not a Code state (Texas) so I'm not sure what ramifications of declassifing a vessel in some code states would be.