There are no significant die varieties known. The mintmark is tiny and placed fairly low in the field over the middle of the right serif of the N in TWENTY.
Most 1870-S Double Eagles grade Very Fine to Extremely Fine. This date becomes scarce in AU55 and AU58. Mint State 1870-S Double Eagles are rare.
Condition Census: An 1870-S Double Eagle which grades Choice MS62 qualifies as a Condition Census example of this date.