These are a project from way back, an historical reproduction of Thomas Jefferson's invitations to a dinner at the White House to Mr. James and Dolley Madison. We printed the frame with text, not on a letterpress as it would have been but on an inkjet, which on the rough paper produced irregularities like a real press would have.
There weren't premade envelopes back then and paper was expensive and often scarce. Usually one would use the same paper the letter was on and fold it into an envelope packet. The white house however would have been able to spare the expense.