One major variety is the 1800/79 Draped Bust Large Cent (Penny) with the "Style1" hair design on the obverse of the coin. The overdate error features a 1800 date struck over a 1798 date. The "7" shows up under the "8" but the "9" is nowhere near as prominently visible as it is in the "80" over "79" variety. In addition: The design of the hair on the liberty is the older "Style 1 Hair" used without the extra curl above the shoulder (which was introduced in the Style 2 Hair). The Style 1 Hair was last used in 1798.
One major variety is the 1800/79 Draped Bust Large Cent (Penny) with the "Style 2" hair design on the obverse of the coin. The overdate error features a 1800 date struck over a 1790's date. The "79" shows up very clearly under the "80" - especially the "9" inside the "0" as depicted above. In addition: The design of the hair on the liberty is the newer one with the extra curl above the shoulder (known as Style 2 Hair) which was used starting in 1798 and later.