Indeed the Mk XVIIB appellation for British 15-inch AP projectiles was found to have applied to both early war projectiles AND the new Cardonald design. It is not possible to conclusively state which projectile was used in the cited test based upon the text alone. However, given the post-war date of the test, it is not unreasonable to consider the possibility that it was Cardonald projectiles being tested.
For a good essay on the perplexing situation surrounding AP projectile manufacturing in the UK prior to and during the early part of the war and the bureaucratic struggle between the government and the (two) manufacturers of naval AP projectiles, see the article "The End of an Era", Naval Review, 1960, Volume 2. A deliciously convoluted story
> In the pre-war years, the Ordnance Board had a very dim view of the effectiveness of the navy's 15-inch projectiles aginst heavy armor at fighting ranges.
> In 1936, metallurgical examination of projectile fragments recovered after proof firings by the Ordnance Board found that "the physical qualities of the shell body were not as uniform as the makers claimed" The manufacturers denied the charge.
> In 1940, unusual numbers of 14-in projectiles for the KGV ship were found to be failing proof tests.
> In 1942, 15-inch AP projectiles were found to be failing proof tests against armor thicknesses that the 14-inch projectiles were defeating at the same striking velocities and obliquities.
> By 1943, the Heavy Shell Sub-committee abandoned efforts to work with the uncooperative private projectile manufacturers and commenced its own design program (the Cardonald project) which succeeded in producing a projectile that succeeded against plates that had defeated the projectiles of the private manufacturers, did so at both higher and lower striking velocities and at shallower angles of obliquity.
> One closing remark was, however, of interest - "...they (Cardonald) were still a long way from producing a shell which could penetrate heavy deck armor at twenty to thirty thousand yards range, i.e. at angles of descent of 15 degrees - 35 degrees."