If you have email-able photos a call to Stan and company at FWC would get you in the range. Just looking at what's posted here, the rear propane hatch, brand sticker on the front and the storm flaps on the outside are clues, but to which generation except, "Newer than mine" I don't know. If the registration plate is still on it they have the date of mfg on them. Mine is on the lower right rear adjacent to the door jam.
Good luck