What this coin looks like (obverse, reverse, mint mark location, special features, etc.): One major variety is the 1799/8 Draped Bust Silver Dollar with a 9 over 8 overdate. This variety also features 13 stars above the eagle on the reverse of the coin.
There are three major varieties regarding the date of the coin. These include the Normal Date - Irregular Date - and 1799/8 Overdate. The Normal Date is simply the standard date without any errors or major features. The Irregular date is very similar to the Normal Date except for the second "9" in the 1799 date. The second "9" is positioned lower and is oriented more towards the right (turned more clockwise) relative to the first "9". The 1799/8 Overdate is also very easy to identify with a 1799 date struck over an 1798 date on the die - resulting in parts of the underlying "8" being seen within and around the last "9" in the date. The differences between these two varieties is depicted below in the example comparison image:
There are also two major varieties regarding the reverse of the coin - particularly the number of stars featured just above the eagle. One variety features the standard 13 stars and the other is actually a corrected error featuring 15 stars. The engraver accidently added 15 stars and then tried to correct the error by enlarging the size of the first and last clouds to cover two of the stars up. Although there are still spikes from each of these stars protruding from the clouds - which helps us identify the variety. The difference between the 13 stars vs 15 stars reverse is depicted below in the example comparison image:
Coin value chart: Typical coin prices, values and worth in USD based on grade/condition