What This Coin Looks Like (Obverse, Reverse, Mint Mark Location, Special Features, etc.): There were multiple varieties of the 1807 Draped Bust Large Cent (Penny). The first two deal with the 1807 date on the obverse of the coin - both of which are actually 1807/6 overdate errors where the 1807 date was struck on top of an 1806 date. This resulted in the underlying "6" seen clearly visible under and around the "7". One variety had a larger number "7" and a pointed tip on the number "1". The other variety had a smaller "7" and a non-pointed blunt tip on the "1". The difference between the large 7 vs small 7 (as well as the pointed 1 vs blunt 1) is depicted above in the example comparison image.
Two other varieties deal with the size of the 1/100 fraction at the bottom of the reverse of the coin. One variety had larger numbers which had much larger points or notches extending from the tips of the number "1"s. The other variety had smaller numbers and barely any pointed notches on the "1"s. These features and the differences between the large fraction vs small fraction can be seen in the example comparison image of the coins below:
One other variety features a die defect on the obverse of the coin which resulted in a "comet" shaped feature behind the liberty's head and extending to the rim of the coin. Hence the name "comet variety" is used to describe this coin. This is depicted by the arrow in the example image of the comet variety large cent below: