"EXPANSION BELLOWS MOLLER-BALG" made of "FLEXIBLE THERMOPLASTIC PLASTIC".
I thought that bellows were not applicable to quarter-turn valves, but the title of the drawing is "EXTENSION PASS-THROUGH FOR CRYOGENIC VALVES - SPECIAL MODEL FOR BUTTERFLY VALVES" (and the piece in object seems to be placed on the top of a "COLD BOX CASING").
In any case, I wasn't able to able to find any information searching the internet for "MOLLER-BALG" or similar...
Bellows seal valves are essentially valves which are less likely to have fugitive emissions problems by containing the valve stem mechanism in a bellows. Thus a valve stem packing leak will not leak to atmosphere. Due to the required flexibility of the bellows, the stems of these valves are LONG. They can be designed in for new construction, though that can be painful. Retrofitting into existing installations can be virtually impossible due to interferences.

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