That's a very strange item. It is cut exactly like the Type 2 S2000 camo slangvel, except that it is missing the epaulettes, and of course the donkey tail. So, the cut of the smock makes sense if it's a Fieldswear made item. I can see the tag on the liner, but is there a tag on the slangvel itself? The zipper also looks too small, and not the big, chunky type found on the issue items.
If it's an actual Fieldswear marked item, then I would lean toward this being either a test or sales sample of some sort. The SANDF has never used the US chocolate chip pattern, or even considered it to my knowledge. The slangvel is a very SANDF specific garment, worn with pride by the Parabats, so it is highly unlikely this was made for a foriegn contract. As such, I would think this was a test sample, or the product of a couple of the tailors mucking about on the production floor with some non-standard fabric.
It's certainly very unique!