Old mid-century 1950s vintage, industrial Barksdale pressure or vacuum activated switch, model D2H-H18. This switch is from the estate of an industrial engineer who had salvaged it from an old installation for building a driveway alarm signal, the kind where the car drives across the tube and it rings the bell.
This switch is made to switch with either pressure or vacuum on the control port and is adjustable from 0.4 PSI up to 18 PSI. It is rated for .5 amps at either 8 volts DC, 14 volts DC or 28 volts DC. It is also rated for 10 amps at either 125 or 250 volts AC or 3 amps at 460 volts AC.
This has some wear and soil.