Dirty Gold Sovereigns, clean or not?

Sorry but that's bad advice. While lemon juice is acidic and will remove some things, it is also organic. And you never want to use organics to clean coins.

Nor do you ever, ever, ever, want to wipe a coin with anything. Or brush it, or rub it, or do anything of the sort. You don't ever want to even touch the surface of a coin with anything ! Not ever !

There are only 4 things that should ever be used to safely remove something from a coin.

1 - distilled water
2 acetone
3 - xylene
4 - a commercial coin dip

Each of these things has different and specific uses, depending on what it is you are trying to remove from the coin. And each should only be used when you are trying to remove those things, and only those things.

And with the first 3 of them, all you should ever do is either just rinse the coin or soak it, again depending on what you are trying to remove. And with the dip, you only dip the coin for about 1 second and immediately remove it.

And all 4 must be used correctly.