If you're willing to do what I'm about to tell: Take a glass/plastic bowl, layer it with aluminium foil, lay the coin in the bowl in such a way both sides are exposed, now pour boiling water and baking soda followed immediately, and let it cool for a while. Now take the coin and gently rub it with a tissue and wash off any residue.
I’d say no. They look like they are down to the bare metal surface and any further cleaning would only make them worse. The latter has silver wash that definitely should not be tampered with. I personally wouldn’t consider buying these coins anyways; there’s better condition ancient coins than these out there that won’t break the bank.
I'm afraid not, if you were willing to get a stereo microscope and spend some time under there with precision tools (tooth picks, dental picks, etc.) you might release some small amount of crud. But to be honest, anything you manage to get off under a microscope you won't notice with your naked eye. These coins look pretty well cleaned and won't release any more detail than they already show. I definitely wouldn't tamper much with the first one, I would be very concerned about that crack seen clearly on the reverse. Boiling/hot water especially would compromise it. If you are into cleaning coins there are plenty of threads on this forum that discuss it in detail with good guides and references to good/decent sellers. Just search for 'uncleaned' and you should find everything you need. Otherwise, Like ValiantKnight said; there are loads of great looking coins out there for cheap if you know where to look. Good luck!
Tough to tell if it’s horn silver from the pics. If so. Sodium thiosulfate removes horn silver very well. Dissolve some STS in a jar and soak overnight, and the dark spots will disappear. Be aware that chemical treatments may erode the high points of the coins. I’ve found that lye will soften details in billon/silver coins. STS generally doesn’t impact the fabric of the coins, but may lead to a rather dull gray appearance
Agree. The coins are corroded. Further cleaning will just worsen the situation with them. They need to tone down over time (a very long time). The silver needs to darken, and it will, so the overall color is more even. The coins will look somewhat better, but the corroded surfaces will remain nonetheless. Try storing them in paper envelopes and check on them periodically.
I didnt buy them. I was mainly checking future reference. Kinda trying to get the feel for buying conditions of what might be cleanable