i looks for information about practice/training versions of UK No.16 oval pattern grenades.
I have one piece without thread in bottom hole, [top hole have a thread 15mm for polish training fuze - threaded in Poland in 1920years] lot grenades no.16 useds in PL as training type.
Shell not have a signatures of production, and not have a forced fragmentation grooves inside shell.

diameter 55mm, length 85mm [typical shell have a 90mm].