The Longacre obverse without stars combined with the 'Standard Silver' reverse of 1870. This design was apparently implemented by William Barber after Longacre's death in 1869.
These were sold as part of complete sets from the half dime to the silver dollar. To view the set, click here.
The illustrated example is one of the rare aluminum strikings with fewer than 3 confirmed to exist.
This also exists in silver J1059/P1194 with about a half dozen known and copper J1060/P1195 also with about a half dozen known.