D6 blade ID help

Thanks Old Magnet! In the ACMOC library, there's a parts catalog for the No 6 Toolbar, 76C1-up. The diagram on page 8 is very similar to the one you linked, and includes 1J509.

I am new to heavy equipment. What does the "ag only" on the blade mean?

Thank you d2gary, I think you are on to something. From what I understand, the machine was used for road maintenance and snow removal the last 10-15 years.

This morning, we walked around the property where the machine currently is, and found a second blade. Can anyone id this blade? It's 95" wide, and ~81" from the top of the blade to the end of the mounting arm. There's a little yellow paint on it still but not much.

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That looks very much like a Dakota blade. A after market brand from 60's to 80's. Just guessing, this second blade is the width for a wide gauge rather than your narrow D6.
Looking at the turions on your tractor it looks like the second blade arms would fit if the current arrangement was cut off of them.

My first thought was your blade had been extended higher to push loose brush like orchard pruning's. But if improving a blade for that teeth on the bottom like in d2gary's avatar picture would be more important in my limited experience pushing pruning's But once pointed out the piling of silage make perfect sense for your blade. I would not want to guess just how tuff your current blade is. But have seen some ruff and tumble operators beat on a Dakota blade and not break it. But it was weeks of work not years..