No discussion of bicycle messenger bags would be complete without a mention of Manhattan Portage! Their website says "since 1983".
My personal opinion is that the messenger world took a turn for the worse when Timbuk2 discontinued their cool REFLECTIVE bag because the Scotchlite material was urethane based.
I have 3 or 4 of them "in stock" - taking offers :- )
Mark Petry
Bainbridge Island, WA