The 'A' identification is on older golden books near the spine in the back of the book. I believe the books you mention with a Roman numeral date are later books , 24 pages long. This type of book had an 'A' before the Roman numeral date for a first edition and no notation of later printings. There are many other ways that books were marked depending on the age and price.
Hi Goldhunt, I understand about the letter system for editions, ie "A" etc. I have many of these. I also have several that just have a copyright date and NO other date at all, and NO letter printed. Others have a copyright date and a Roman numeral date but NO letter before it. Does this mean that these books are a first printing then, and therefor an "A" edition? Would appreciate your help on dating these books as they are for sale and I do not want to misrepresent them to collectors.