I have to add some fuel to this discussion. Great information.
I have a document from the late historian D.L. Allebaugh. Includes history of the hearse including all owners and summary of "U.S. Compound No. 1."
The document also states..
"Year Carriage Was Made: 1850 1 of 3 of 13. "
Are there any original images available of the Hearse that carried Lincoln from Peterson House to Washington, then to the train station? That would clear up a lot about the hearse at the Gettysburg museum.