Dave,
If it is for Match Rifle, and as such has a boat-tailed bullet, it should have the letters "SL" [for "Stream Line"] in the headstamp, and be made by Kynoch. However, the specimens that I have seen all have the two-digit date.
I have seen similar rounds made by Greenwood & Batley, with blackened head, and 4-digit date (but only 1938), but I have not been able to find out the significance of the black stain. Kynoch seems to have had a monopoly of supplying ammunition for the "Match Rifle" competitions at Bisley (they donated all that required for the competitions in the "Hopton" Aggregate), but I suppose G&B could have tried to provide such ammo for the shooters for commercial purchase, but I have never seen a box that indicates this, or seen any other evidence to suggest this was the case.
Roger.