3.7" AA shell maker? Australian or South African?

This 3.7" AA shell is currently up for auction here in Australia.

As it’s located in Australia and stamped “BHP” (a large Australian steel supplier), I initially thought it was Australian. But now I’m not so sure. It appears to be stamped with a broad arrow inside a “J” or possibly a “U” - Union of South Africa?

It’s dated 20.1.41 and the maker appears to be “S&? E”. (If I had to guess I’d say S&C E.)

In early 1941 the only manufacturers of large calibre projectiles in Australia would be government munitions factories, and the only one making 3.7" shells would have been Maribyrnong Ordnance factory (MO monogram). It has no MO stamp and I have no clue who S&? E is.

So I’m stumped with the maker and country of this shell. Any ideas?

Cheers, Graeme

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