If it is rating (pressure temperature), you may refer ASME, google and you will find link. There are already too many discussion on CR4 on this subject. Go to search CR4
If its is something else spell out.
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Fantastic ideas for a Fantastic World, I make the illogical logical.They put me in cars,they put me in yer tv.They put me in stereos and those little radios you stick in your ears.They even put me in watches, they have teeny gremlins for your watches