silver nuggets

Can anyone tell me if they ever found silver color nuggets with roman numerals on them ie x l c m d etc. Also have SI and all are in shape of pigs, upside down is boat. Maybe something to do with Tom Tew or his men? nearby were rings with 925 and IC K inside also with pig logo. Could this be a lost hoard?  they appear after a NorEaster at low tide consistantly. jewelers say they are not sterling too soft, could they be pure? all look like old dimes or pieces of 8 in color. Some are rusty and very salty look very old. when some come out of water gold color quickly turn brown electrum? i need help as coin stores say they are melted aluminum. i have hunted 40 years and know what pull tabs look like. HELP!