Hey everyone, I recently received 3 "4 reales" coins from a person claiming his grandfather found them with a metal detector. I saw the porousness, and was hoping they were dug/water salvaged coins - but upon opening the 1807 coin, and giving it a good ol' fashion flick in the air - its a 100% dull THUD , and the porousness leads me to believe these coins are cast? He also sold about a dozen other coins, of many types, all with the same look Can a ground, or sea salvaged coin have no audible ring to it?? As a reference, i've included two coins that I did not purchase, but were recently sold by him (there were several others, mostly Bust Halves, a couple mexico 8 reales) The variety and aged look to the coins leads me to believe perhaps they were ground-dug , or he collected contemporary fakes (which apparently is a thing) I'm stuck as to whether I should return these 4 reales coins, they just do not seem like silver from the sound and look. Thanks so much for your help!