This seems to be a duplicate made from the original Ambrotype. If it is a period duplicate Ferrotype (Tintype) I cannot say from these images. Although it would not surprise me if it was made long after the original plate was made. Therefore I cannot make an estimate. This has to be seen by an expert in person.
If William Frank Browne made copies in Ferrotype/Tintype is not known to me.
I do know Albumen prints have been made by him of George Custer.