Field sketches that instead of showing the standard call out for valves (i.e. 150# etc) what I'm getting; for example, 275WP or 275WOP and 275WOG. What is up with WOP and WOG?
275WOG would indicate that the ball valve is rated to 275 psi cold working pressure.  As hydrae said: Water-Oil-Gas,
275SWP would be the rated Steam Working Pressure (Saturated) on a device so stamped.
ASME 150, 300, 600.....4500 are very specific and meaningful standards.  Individual alloys are identified and rated for different pressures at different temperatures. You have to look in the tables, tho'.  This is now an ASME standard (B16.34, B16.5) Was known as ANSI B16.5, and 34 previously and still predominantly referred to as ANSI specs..  Long ago, was known as ASA.

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