FD, is this a pic of your tractor or one you found on the net? That rear end doesn't look anything like the rear of the tractor that you posted earlier.
This one has the mounting tabs for the tiller coming off of the frame, while the first one had the mounting tabs in the axle.
That "silver rod" is not a rod, that's a WIRE CABLE, and it would be connected to the tractor's rock shaft for raising and lowering the tiller.
I looked through some of the manuals I have and some in the manuals section, and I think that the tractor in this thread is one of the 5000 series. That rear end doesn't look anything like the rear end of the Q-Series.
The mounting for this tiller mounts with a pin through a single tab coming from the tractor's frame. The Q-Series tiller would 'hang' on a pin that goes between TWO cast tabs that are a part of the transaxle housing.
That is a Bolens Duratrac. It is a clevis pin on the end of a cable. It is OEM. I am guessing the engineers never thought anyone would want a rear attachment with thier Duratracs (GT2000), and GTX's. There are three different sets of brackets that they deveoloped for attachments. The 3pt hitch brackets are different from the tiller brackets, different from the rear weight bracket.
The pic with the Tiller is a pic I found on the web. I mistakenly thought it was a QT19 like mine, But alas you all proved me wrong. Thats why I joined here, to help me learn. I hope to make a 3pt hitch for my QT1900 at some pt.