I don't know this one. If it is 6.5 inches across centres it is probably British. Does not look like Williams, Phillips, Nicklin, Chater, or BSA, the only double fluted British cranks I remember were BSA.
I recall similar ones on my old trike in 1968. I think that was a TA 5 pin cottered set, if I remember correctly. It was a b***r to set up and had smaller OD cotter pins than standard english ones.