Ron Guth:
Only one 1798 Dime variety shows the Large 8, but this is a bit of a misnomer since the size of the 8 is actually quite normal relative to the other digits of the date. Rather, the size of the 8 is Large only with respect to the Small 8, which is indeed tiny. Thus, for eyeball attributing, a side-by-side comparison (such as in the attribution image above) is necessary.
The Large 8 variety is known as JR-4 and it is relatively scarce in all grades. However, numerous Mint State examples exist, filling the Condition Census from MS63 to MS66. Speaking of the MS66 example, that coin has not appeared on the market since PCGS graded it in 1989 (to our knowledge).