We have seen these before on handclutch MKDs. They cut off a BJ 11 left side shift lever and brazed it to a EJ 47 side lever. Later Nethercutts and Rokons use a longer EJ 47c side lever. It was painted Hunter green on the EJ 47 end and still had the original chrome on the BJ 11 end.
It is fastened with a EJ 48 nut that has a 3/8-26 BSC (British Standard Cycle) thread.