This is a PMP remanufactured Southwest E-400-3 Meter. It is for 4:1 gallons applications and can be identified by a flat outlet on the bottom (as opposed to the chamfered outlet on a PMP # 24003) and stamped metal adjusting dial assembly. PMP remanufactured units have a pulser mounting bracket.
These meters were originally manufactured after mid-1986 and was used in Schlumberger® 4000 series dispensers.
This meter can be used as a replacement for the discontinued PMP # 24002 E-400 "Old Style" Southwest Meters which had a hexagonal cap over the adjusting mechanism.