Hi dansblackcat, and a warm welcome to the forum. It's great to have another Scott Bonnar owner on board.
We all like to learn new things and tinker here, and this particular machine is no exception.
Just when I thought I have seen all the models manufactured post 1950, here we are with a model I never new existed. I have never heard of, let alone seen one before. This is a rare beast indeed!
You are correct in your assumption, it appears to have been based on the Model 40 chassis, there may be a model number stamped on the brass ID plate riveted to the back of the battery charger, that may pin it down. It appears to be a 14" cut, and if it is part of the Model 40 family, it would have been manufactured around 1960. So it is an oldie.
Re: the bracket, I cannot see where it would fit or more importantly what purpose it would serve.....my only thought is you may be correct, it may fit where the lower handle-bar attaches to the mower; so that the machine can't be tilted so far backwards.... maybe to prevent battery acid from spillage through the vents in the cell caps???
Parts are extremely hard to come by for a Model 40, and in particular the catcher....a Model 40 is the only one that will fit your machine particularly because of the way it attaches to the machine....the catcher hooks fit into the two vertical slots just in front of the grass deflector.
I sold a Model 40 in very good order because I couldn't beg, steal or borrow a catcher for it.
It is a rare and unusual machine....well done and a great score!
