Cleaning Silver & Gold/Silver Japanese Coins

Nothing wrong with posting only one side but in most cases it is beneficial to show both sides - either for the beauty of seeing both sides of the coin or to provide a proper judgement. Was not meant as a criticism but rather a recommendation.
(When you look at my topic on official countermarks, I have shown several times only one side because the other side was not important to the countermark [and had nothing else going for it].)

The lead coin I HAD was acquired many years ago.

It was a fake ancient denarius of Julia Paula, bought from a dealer in the U.K.
I didn't check it for authenticity, and it was revealed to me by a Sydney dealer, by bending it with his fingers.
I thereupon gave it to him, to add it to his reference fake ancient collection.

Occasionally, I will test a suspect freshly made lead coin by bending it. No loss in value if you damage a fake coin, and a genuine coin will stand up easily to this simple test, so no loss either way.

Sometimes the alloy is of pewter or lead / tin, and they are a little harder to bend, but they stay brighter for longer.

There is no problem from this viewpoint in this case, however.