Sure looks like one.Post-war. Looks like he is wearing a M1885 frock.
I believe you hit the nail on the head.
The split cuff is a feature common to ACW era Federal trousers.Lovely image @Majalu72 Is he a relative of yours?
Interesting - the slit in bottom of the trouser leg ......my son and his age group probably thought they invented that.
Has anyone seen a split trouser leg in an image earlier than this one?