Butt Marking on a No8 Mk1

Got a few No8s recently one has the following butt marking:
BW
S
3
58

Any one know what it means ?

Attachment 58987Attachment 58986

40 Base Workshop Singapore March 1958. It was known as Singapore Base Workshop then and changed to 40 Base in 1960 or so and the indicator changed to 40BW - S and the date. We only saw very few No8's in that theatre. Some were mounted on the side of the big 120mm Combats and Wombats as sub calibre trainers under local arrangements for limited training as the only full size anti-tank ranges in the whole penninsula were at Asahan ranges. Strange but true, the hard targets were all old Japanese tank hulks and re-captured (back from the Japanese) bren gun carrier hulks. Realistically, the use of armour there was a lost cause!

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Thanks Peter, just adds that bit more real history to the rifle