Cast counterfeits have many common characteristics:

Poorly formed lettering (and stars)

Grainy fields

Lack of detail in areas where fine detail should exist (cotton blossoms, large and small bear claws, hair curl over the ear, etc.)

Uneven denticles and debris between the denticles

Tooling marks (behind the eagle's head)

Polishing marks (to buff out the grainy finish)

Casting seams around the edge of the coin, sometimes obscured by after-added milling, usually from a Castaing Machine or similar device

Edge milling that is too sharp or wrong for the type of coin

Improper weight

In the case of silver, failure to pass the "ping" test

In the case of copper or silver, failure to pass an Eddy Current Bake test

Failure to pass a specific gravity test*

Greasy or discolored surface appearance

(Sometimes) obvious plating of the cast core

Mismatched die pairings (such as impossible
VAM varieties)
The use of 3D printers and plastic molds makes more recent cast counterfeits better, but they are still pretty crude copies.
*Chinese counterfeiters frequently use 87-88% Sn and 12-13% Zn cores with 90% Ag 10% Cu plating for their counterfeit Morgans. This composition
very closely matches the specific gravity of a 90% Ag 10% Cu coin, so specific gravity alone isn't enough to verify authenticity of a silver coin. While these fakes can fool specific gravity tests, they miserably fail the "ping" and Eddy Current Brake tests.