Is the blower 6 or 7 feet? It looks to me like a bit more than 6 1/2.
The auger attaching to the extenders is uncommon, but I have seen it before, mostly on old McKee blowers that had the solid auger and somebody changed the auger on. It works fine if done well.
The gearbox on the blower is a very common old snowblower gearbox. It may be a Hayes-Dana but I don't know for sure. I have seen that same type of gearbox on McKee, Allied, older Lucknow, George White, Walco, and others besides those. The through shaft on the older ones is 1 1/2" with a 3/8" key at the PTO side and 1 1/2" with a 3/8" key but sticking out further at the fan side with a 5/8-11 or 1/2-13 threaded hole in the end. The side shaft is 1 1/4" 19 spline. Most of these gearboxes I have seen have have the through shaft seals on the shaft but a few have a wear sleeve pressed on where the shaft goes through the seal, then making the shaft 1 3/4" at the seal. Inside the gearbox they have tapered roller bearings and are adjusted with shims and staked nuts on the shafts. I think the gears are cast iron but some may be cast steel. Replacing the seals is fairly easy, unless someone has welded on the PTO yoke, welded the side shaft coupling when it wore out instead of replacing it, or if the fan is jammed on. Make sure you have a seal puller, it is well worth getting one for this job. Removing the gearbox depends on the auger and fan set up but many times it is easiest to remove the side shaft, unbolt the bolt in the center of the fan (usually 5/8-11 or 1/2-13), remove the 8 gearbox bolts and pull the gearbox out the back (it is probably 40-50 lbs and will make your hands smell of gear oil for a day). Getting the gearbox back in can be a trick, it helps a lot to have another person to hold up the fan to get it lined up with the gearbox shaft. Also, grease the fan shaft so it does not seize to the fan and don't forget the key in the shaft.
If replacing the seals on the gear box looks like it would turn out to be very difficult, fill it up with corn head grease and some heavy gear oil mix. That will not leak much even if the seals are bad and will let the gearbox last a quite a long time yet. I have seen grease in gearboxes with bad seals that had ran that way for many years with no more noticeable where on gears or bearings.
A couple tips on the PTO shaft is where the shear bolt holes are on the shear yoke if they are not round and more oval that makes the bolts more prone to loosening and breaking. In my experience one 3/8" grade 5 bolt is more than enough. Make sure to use nylon lock nuts as for some reason lock washers seam to still let them loosen. Still on the shear yoke, there should be a snap ring that holds the PTO shaft tube in when the shear bolt breaks. If there is not, some times it could come apart when a shear bolt breaks. Also check that there is enough overlap on the PTO shaft at all height positions. This is mostly a problem when the tractor and blower are parked outside, but one more thing about that PTO set up with the tube on the blower side, is water can melt down the shaft and accumulate in the base of the tube, then freezing to ice and pushing the yoke forward on the tractor when you raise the blower and the shaft has to retract. The solution to that is to drain the PTO every warm day or swap the U joint positions so that the tube side is on the tractor half and is always sloped down when the blower is down. I think there is a good chance a drain hole would get plugged with grease or ice.
As far as any thing else to check before winter, the bearings on the auger and at the end of the side shaft, sometimes they are sealed and other times they have grease fittings. The chain master link, particularly if it has a offset link in it, those tend to be the first to go, especially with a bigger auger. Make sure to have a few spare links. The shear plate sprocket on the side shaft, if it has a grease fitting make sure it is well greased, on some old ones there is not, make sure to keep some oil on it. If the shear plates get stiff then they will break the chain before the bolt.
Tractor tire chains might be a good thing to have, some winters without much ice it is alright but a bit of ice or hills and it can be tricky.
Independent or live PTO is one of the most important things with a snowblower, after a good water proof jacket if you are on an open station tractor. Low reverse gears are good too, tractors with only high reverse gears and low power are difficult in deeper snow.
One other thing on the snowblower chute is many chutes that have been hacked at, there can be certain positions where there is a small amount of snow going straight up and then landing on the tractor. It is hard to tell if that is a problem until there is snow on the ground to blow, but I have had that be a problem on some blowers.
I am not sure if these older McKee blowers had replaceable cutting edges or not, but most of them have been worn out one way or another by now. A piece of 1/4" X 5" steel strap stitch welded or bolted will last many years. For the first few blowings of the year, shortening the top link will leave a lot more of the driveway on it instead of the lawn, particularly if the ground is not frozen yet.
