Curious 'original' red canister in heater core hose line

[roverp480]

Certainly looks like a coolant heater. Mains 120V 50/60 htz AC . I have seen similar units here in the UK . I wonder if it has a pump in it to circulate the coolant or relies on thermo syphon to generate flow. Either way will also heat the block to some extent
I have an original Rover supplied block heater in my vehicle , screws in place of the alloy plug just above the starter motor . 240 volt as its the UK but they did supply a 120 volt one for export.

[slowpatina]

Thanks @roverp480. Seems we're on the same page in thought. Will likely leave it in place simply because it's original as is most of the truck. If it ever rusts out then it can be removed and the usual heater core feeds would still be in place.