It does not look original. Neither is the in-line fuel filter, but that is a good addition.
Trace the wiring to see where the other end goes.
With the pipe connections, and electrical connection I would expect it to be a shut-off valve.
1. Fuel, was going to be set into the fuel line to shut off when engine stopped to prevent the engine running on after ignition turned off. (Most likely)
2. As above but an anti-theft measure.
2. Breather, to close the breather to prevent blow-by gases being ingested an burning at certain times. Unlikely, but I have seen this on something many years ago, but more likely on old diesels. The valve looks too small for this.