I have this 1842 seated Liberty dollar that seems to have an 1875 eagle on the reverse. Interesting. It screams 'fake', but . . . . . . . . ? I have heard that some of the 'later' coins were 'overdated' with an earlier date. 38 mm (appr.)., 20.04 gm (appr.)
Your first instinct was right, its a fake of the morgan reverse design mixed with the seated liberty style obverse
But nothing, unfortunately... this one screams fake, ahem, "fantasy piece" so loud it'll blow out the eardrums of everyone here.
You guys have it all wrong. It's a product of time travel experiments from the unmentionable area in Roswell. Steve