What this coin looks like (obverse, reverse, mint mark location, special features, etc.): One major variety is the 1806/5 Draped Bust Quarter. This variety features an overdate error with an 1806 date struck on top of an earlier 1805 date. This resulted in a "6" over "5" overdate. It is easy to identify this coin by very clear portions of the underlying "5" being seen within and around the "6" as shown in the example image above. Source of example image is courtesy of Heritage Auction Galleries.
Coin valuation chart: Typical coin prices, values and worth per grade or condition - in USD