A valuation of $19,200 for a 1976-S Bicentennial Quarter in silver, regular strike (non-proof), is exceptionally high and would need thorough verification.
Bicentennial Quarters were primarily minted for circulation and do not contain silver. They were made from a copper-nickel clad composition, like other circulating quarters of the time.
It's possible that there's confusion here or that the coin in question is an error or a special variety. However, if we're talking about a regular circulation strike Bicentennial Quarter, such a valuation would be unusual.
If this price is indeed accurate, it would likely indicate a rare error or a misidentification of the coin.
In such cases, it's essential to have the coin authenticated by a reputable coin grading service and verified by experts in the field to confirm its authenticity and rarity.
Always exercise caution and seek expert advice when dealing with high-value coins to ensure that you're making informed decisions.