An external oil pressure relief valve on a Ford 100E unit ... an ELVA connection as on one of the ELVA/LRG IOE converted engines ... any ideas? Could have been sourced Stateside and from the casting might be AN?O or EN?O.
Thoughts appreciated.

Malcolm Buckler has solved the mystery..
" It is ENFO Roger. It is simply the bottom casting of Ford 100E oil pump. The bit that houses the pressure relief valve. This, with a few mods, is fitted to the valve chest cover. A plate is made up to seal off the end of the oil pump. Then the owner has access to the pressure relief valve without removing the sump....in my case, removing the engine. With thanks to Mr Parry-Jones, who explained this on the Facebook Buckler Cars and Karts web page. "

A very speedy response.. that rarely happens!!