Vintage Butterscotch Simpson AS2A - Satisfaction

Yes: it was ME that bought this beauty from that well-known auction site. I was the only bidder. Including postage, in US dollars: $175. I saw a used one of these sell for that price 5 years back, so I think it was a reasonable price to pay. I don't really know. Hope so.

This one is in the original box and, according to the seller from the North of England, it was never used. He tells me it was his father's, and that it dates to about 1967 - the same year as The Rolling Stones' "Satisfaction". And yes, I am satisfied.

I am far from an expert on these brushes, and I believe they were part of an original M series (?) I have also read different accounts of the  meaning of the lettering, claiming that the "AS" means "Alex Simpson" (founder of Simpson brushes) or "Abraham Strauss", for whom the AS series was manufactured. Very ambiguous. 

I know there are AS2 brushes and AS2A, possibly others with the 'crown' or 'lip' at the top of the handle. I don't understand the difference, and was wondering if anyone could point that out, or show pictures side-by-side? I think perhaps the AS2A is longer. Maybe it has a different knot?? Does anyone know anything about the history and evolution of these lovelies?

Pictures (with more to come when I receive it here in Sydney from the UK, and clean and smarten it up):