No, what the sovcit attached is called a bullion coin. They usually have a nominal value, so they are official legal tender and you can pay with them in a store, but their actual worth is basically the price of the precious metal they are minted from (+collector's value for some coins) which is usually much higher. 0.9 troy ounces of pure silver are around $28.

It is the coin holder's duty to liquidate the coin before payment, so the sovcit basically just scammed themselves and gave their coin away for the nominal value (although it will likely be returned as this letter will not be accepted for obvious reasons).