This Medallion which weighs some 12 grams is stamped to the reverse .925 (which denotes Sterling Silver)then SILVER and RMP. I am not sure what the RMP is for...maybe Royal Mint Pretoria?

A nice South African item of Silver.
"Quartermaster's Comment":-    To the fore we have a typical 'Boer' kneeling with his rifle in readiness. The letters U. V. M. and U. D. F. indicate its use by the Union Defence Force......Whoever won it did not have his name engraved on the back.
It probably dates for the period between the wars.