some great reference info Layla put together for us:
The Classic Flap Bag comes in three sizes:
Small - 9" x 5.5" x 2"
Medium - 10" x 6" x 2.5"
Jumbo - 12" x 8" x 3"
There are four sizes in the Reissue 2.55:
A302224 - The Baby ?
A302225 - The Medium 9.75" x 7.06" x 2.16"
A302226 - The Large 11" x 8" x 2.5"
A302227 - The X-Large, Jumbo aka A-4 size 12.25" x 9.18" x 2.5"
I think there are FIVE sizes in the reissue and I'm pretty sure they make a 228.