These are two mirror-image prints, with the Van Houtte (right) copied from the Curtis. An engraver likely made a copy onto a copper plate, using the print from Curtis as the model. When the plate was inked and used to produce prints, the image would be mirrored.
Note that the prints are not quite identical, aside from the mirroring. Some details are different in the engraving, and the colors are significantly different.
The Curtis print is the first publication of the species.