Original 4 terminal Lucas 6RA horn relay as fitted to the Jaguar E Type S1 & 2 MK2 Daimler V8 plus others, part number C17338 or Lucas part number 33209 and dated June 66

it's been tested and works just fine (it's a normally open relay)

Aftermarket reproduction items are available for about £35.00 but as always there just not the same as an original.