Actually, almost all of the ones that were built up to the 90's came with a 12 vent roof. It's the upgrade that has them switching to a six vent roof. in the pictures I posted, both MKT's are 85 models, but Dave's was modified under a contract that rebuilt the whole thing. The six vent models have a better (read safer) vent opening mechanism. Mine was modified for the MBU electrical system but has none of the other enhancements.
In Arlen's second pic, notice the ring at the lower left, that is a rubber rain guard that is supposed to go near the top of the corner post to re-direct water that drips through down onto the post instead of out in the middle of the walkway (we had some rain and I found out the hard way about that feature).
MKT's came in the following models (that I know of): 75, 82, 85, 85S, 90, 99 and -I (for Improved - meaning all the mods were done at the factory, before it left). The fan is indeed for cold weather, as it redirects hot air from the ceiling down a flexible pipe to a vented pipe that is installed under the kick cutout on the field range side - keeps the cooks feet warm in the winter.
If you can preview, just look under the side canvas to see what is inside, without dropping the outer walkway. The more it has in it, the better! I do have some spare parts that are excess to my needs - curtesy of GL auctions (22 short, real canvas, end walls when a single MKT needs just two and the current ones are vinyl). It's a matter of getting the time to go through what I have and inventory it, but there have already been five folks here on SS that have orders either received or in the works. Most items are unobtanium, but if I can help another collector/user and still recover my costs, I'll do it.