Just go to a reputable gold & silver / coin shop. {They will discount what you get by a few points because that is how they make their money.}
worth ABOUT $210.
"I would guess at USD300 "
Why would anybody assume the could sell unassayed, no provenance block of silver at 50% above spot? Spot price is $200. You won't get spot from anybody who deals in any volume and possibly 10% less. Spot price is for good for delivery bullion at bullion repositories which yours surely is not.
I would guess at USD300
Go in person to a reputable coin/bullion dealer. I don't know where you are. London--johnson Matthey, Spinx, Stanley Gibbons. Usually Capital cities have a jewellery/coin/precious metal centre. Like UK we have the famous Hatton Garden.
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I have a block of silver that is 10 ounces of troy , fine silver I want to sell, but not sure how to go about doing so.
With so many sites and out dated information, I cant seem to find anything current. How much would this be worth??