I did some research. It seems all model 36's were transition gun between models 1893 & 336. First one had "A" prefix and was made 1936-1937. First variations were made between 1937-1940 and had no prefix. I therefore think a 36A was first of 2 variations made between 1937 & 1940. I don't think it has any extra value compared to basic old 336 but could be wrong??