Newbie GasGas Owner with some ???

[rpduc]

Hello all,
I just became a GasGas owner (in spades) with the purchase of 3 well used bikes. '03 ec 250. '04 ec250 and a '05 mc 250 purchased as a "lot." I'm going to need to get educated on these things and this seems to be the place so TIA for any and all help.

Above are the years I was given by the previous owner. I get the impression he just rode 'em and didn't sweat the details. The "03" has WP forks and shock but the specs I've found say the '03 had Marzocchi forks and Ohlins on the so I'm wondering...

Anyone know the "codes" in the serial #s that delineates model and year?
They do have d, e and f in the #s respectively so I'm gonna take a wild guess that that is the "year" code?

Also, the "mc" does have a 19" rear wheel and looks to have the correct suspension, but the serial #/vin # has ec in it just like the other two. Should the "mc" have a mc in the numbers?

Not that I care all that much, but it would be nice to know exactly what I got.