Question about uniform golden toning
I have an 1830 small O bust half dollar certified and graded by NGC as AU58. The coin fits the grade well with nice, cartwheeling luster over the fields and devices except for the high points and some more subdued luster above the eagle. It also has very uniform golden toning over the entire coin except for the high spots. The toning is such that a non-collector might even mistake it for a gold coin.
I suspect it's been dipped and allowed to retone but I cannot tell from the luster that it's been dipped. Is there any explanation for how this uniform gold toning could come about? Sorry, I have no pictures of this coin to show.