Hey Greg,I’m no expert on the 499 and that is why I called my timeline Unofficial. The changeovers could have spanned years. Regarding the 499A; I think the jump was from 499 to 499B. However there are the occasional 499A stamped models that show up. Just last week on EBay I saw a 499A offered, and based on the photos it was definitely stamped with 499A but it looked NO different than a 499B. No explanation. Weird huh?