Until 1964 the US issued paper money labeled “Silver Certificate” and redeemable for silver dollars or (briefly) silver bullion. Redemption ended in 1968.
FWIW, silver certificates are still legal tender. You can spend them, and they are worth face value. You just can’t exchange them for silver anymore.
The UK mint regularly issues gold crowns. The latest one in 2015 when the Queen became The Longest Reigning Monarch. Until the 90s they had a face value of 5 shillings (25p) but that was changed to £5.00.
The Royal Mint makes a good profit on these commemorative coins and the silver proof coin (Sterling (.925) Silver 28.28 grams) was sold for £80. The gold (Gold Proof 22 Carat (.917) 39.94 grams) was priced at £1550.00.
These are real coins and if you were foolish enough, you could buy £5.00 worth of groceries with them at a local supermarket.
There were 90 million 1963 Franklin silver half dollars minted (alongside 210 million 1963 quarters, which seems like a balance, given the denominational math, and the buying power of the time).
My impression, from coin-collecting sources, is that the coincidence of the new 1964 design for the slain, popular Kennedy (which people pulled to ‘save’), and the move away from silver immediately after, is what caused the original scarcity of silver halves. By the time silver was all gone, it was inertia; people had adjusted to counting change without halves.
More realistically, as far as the cashier is concerned, it’s “Wait, what is that coin? Is it real money? Hold on, I need to get a manager.”.