Well I've seen a lot of odd British industrial and military connectors, but never one like that. Having said that, that arrow mark looks very much like the one used to identify WW2 era military stuff, though it would normally be on the rating plate too. What did you find it on?
Definately domestic. I have seen them around here in Florida many times. I just can't remember where I've seen them or who makes them. I think I have seen them on lift stations.
I can't view photobucket from work and can't see the pictures, but if's in a mil-spec connector, I could probably help you identify a mating connector & backshell. Is there an M# on there anywhere? Usually there will be one printed on the backshell and on the connector.