PCGS values a 1966 Jefferson Nickel in MS66 FS as worth $40,000 and the reason is the grade (MS66) and the striking designation “Full Steps” or “FS”. The 1966 nickel is extremely rare when the steps are fully struck and in the grade MS66 it’s a registry quality coin.
PCGS coin collectors put together sets with the highest graded coins for their favorite coin types and denominations and PCGS rates those collections, so they’re called Registry Collections. The PCGS Registry sets boast the highest graded and most valuable and rare coins in PCGS holders.
So when you see a common date coin listed for thousands of dollars then it must be in a high grade and in a PCGS or NGC holder. If a 1966 Jefferson Nickel isn’t graded by PCGS or NGC is it not worth much more than the face value (five cents). So ignore the ads and Google listings for 1966 Jefferson Nickels that some sellers are trying to sell for thousands of dollars but they’re not graded by NGC or PCGS.