These cars are built-to-order by shapeways.com (based on 3-D designs supplied by Eric Cox of Panamint Models).
Here's what Eric has to say about them -
Referred to as Mister Lincoln's Chariot, this Jackson & Sharp 14-window design from cira 1859 was common on Pennsylvania and New Jersey lines. It was remodeled with a monitor roof, but is similar to cars shown in a purported photo of Lincoln's train at Hanover Junction en route to Gettysburg.