The Wanderer-class has appeared only as a graphic on computer screens in several early episodes of The Next Generation. The accompanying text is not clearly legible, however, the design was taken from materials developed by FASA for their version of Star Trek: The Role Playing Game as the Orion Wanderer (gaming miniature No. 2522). At the time the image was used, upside down, the role playing game was considered an "official" source.
As this class was seen on a mission order sent to the USS Constellation, this might indicate that in the canonical universe that this class belonged to Starfleet.