I have an old blade similar to yours which I inherited from my father. I have used it occasionally for almost 50 years. Walked by it in the shed the other day and it struck me that the extra holes toward the top of the blade allow for shifting the whole moldboard to either side by removing the bolts and mounting it using the offset holes. Felt brilliant for about a quarter of a second and since have felt like an idiot for not recognizing that at least 40 years ago. Pretty sure everyone else with a similar blade already knew about that feature.
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EA had a MUCH better (easier to use) idea for blade offset, with their "6 Way Deluxe Scrape Blade".
All gone now,.....but I am thankful that I did buy one of theirs.
I have a new 7' King Kutter, with offset much like this one shown, and it needs another home.