Harold Isherwood Kay's papers were formerly numbered as MS 46 and MS 196.
Material formerly numbered MS 46 (relating to Thomas Gainsborough, John Sell Cotman and Philip Wilson Steer) - The papers on Gainsborough have been arranged into the following folders, it is thought this was done by NPG staff after their acquisition:
-Family attributions to Gainsborough
-Copies by Gainsborough
-Copies after Gaisborough
-Sale cats. Gainsborough
The papers on Cotman and Steer have been arranged into the following folders, it is thought this was done by NPG staff after their acquisition:
-Sale cats. Cotman
-Sale cats. Steer
The material formerly numbered MS 196 is a undated handwritten list detailing the contents of Isherwood Kay's note books, it's unknown who made the list. The National Gallery archive holds the notebooks.