Great original period photo Joe,
Please keep them rolling as most of the older generation who remebered working with these new "U" frame tractors are no longer with us, for us collectors these photos offer so much valuable information for the preservationist / restorer.
As John said, it is the first time I have ever seen reference to an exhaust silencer / muffler, not seen any in the original sales literature of the time.
Also for me it brings back memories of what my dad told me as he remembered many "U frame Massey's" new in this area, he always said front wheel hub caps and rear wheel nuts and lock washers were always painted black.
Looking at this Challenger photo it looks like the Challenger rear axle and wheel taper lock is completely black too? just like the front wheel hub caps. Great to see the fine detail.
Earlier in this thread you asked about the model of horse drawn grass reaper (mower) which no one has answered yet, I will have a stab at a No 33 ???