Okay here's another stab at compiling the data (please double check me you number sleuths)
Leatherman Blast...........introduced 2004
Cap crimper models..............became available in 2005
PAT PEND stamping removed........between June '05 and Aug '06
Molded ledges added to plastic handle liners.............between June '05 and Aug '06
File blade changed around Aug of 2006, but old files remained in the system until at least May of 2009*
Locking levers updated...........between Jan '09 and Apr '09
Nail nick moved to inboard side of knife blade................between May '09 and July '09
*
a theory I made up to fit the data