Man, two Morgans in one hunt, I'd be back at that site real soon. As far as cleaning, first check the value of the coins. (Can't make out the mintmarks) If common date and value, I'd first microwave a small cup of peroxide until boiling, then drop each coin in individually. This is done mainly for copper coins, but won't hurt silver. Then try picking off all that you can pick. Electrolysis works well, but you must make sure that you keep an eye on the coins. Keep us posted!