I feel like it's one of those situations that it would be great to know what really happened, but will be almost impossible to actually find out that information. I can't imagine the consignment company would be willing to give out that kind of information and I can't imagine if it was the...
That looks like the same card being sold on ebay right now. Definitely looks like it was in pen first and gone over in sharpie. This red in auto /66 is signed normally.
I've never looked at the numbers to confirm, but 1968 Topps has a lot. All-Time greats at the ends/beginning of their careers like Mantle, Maris (I know, not a HOF), Ryan and Bench.