I doubt if South Africa ever made 45 ammo. At the start of the war there weren't enough firearms for the envisaged forces contribution to the war and very little ammunition production for what was a minute army. All the firearms were Britishicon. Tompsons weren't in the inventory of the Union Defence Force, only appearing in North Africa and Italyicon. Didn't come back when the war was over.

The ammunition factory was the SA Mint, later Pretoria Metal Pressings [PMP], both still in business but only PMP making ammunition.

As a long time career soldier I never saw or heard of 45 ammo of any age in the depots. Or even of old soldiers talking of Thompsons or 45. Or of them using Thompsons during or after the war. They talked about Stens or Germanicon SMGs.