Check at the back; if it has 2 audio jacks it's a revision A (German model). If it has 3 (left/right/composite video) it's a later west-chester model.
Actually they are not really called B, or even C. Technically speaking it would be a CR (cost reduced) model. To know for sure what revision you have you'd have to open it up.
Judging by your Agnus revision though, you have a CR machine. The Kickstart is a little old though, on Ebay US there is someone selling 3.1 ROMS for 19,95, not a bad deal. (that as high as it will go)
