Waggon-fabrik Gotha was in charge of construction of the Hortens. But OFFICIALLY there was to be no Gotha name on the Project 9 aircraft until production aircaft were produced. Every airframe made or under construction was a prototype. V-2 and V-2 were Horten-built and the V-3 throught V-8 were Gotha-built but still under the RLM's Ho designation
Nevertheless, it was a very interesting and innovative plane under any name.
Here's a few of my books that I consulted:
Bergaust, Erich
Hitler's Secrets Revealed
Bantam Books, NY, 1956
Simon; Leslie E.
Secret Weapons of the Third Reich
WE, Inc. Old Greenwich CT, 1947, USA.
Green, William
Fighters Vols. 1
Doubleday Co., 1960
Green, William
Jet Aircraft of the World
Macdonald, London, 1955
Green, Wm.
The Complete Book of Fighters
Smithmark Publishers, NY, 1994
Green, William
Warplanes of the Third Reich
Galahad Books, NY, 1986
Myhra, David
Secret Aircraft Designs of the Third Reich
Schiffer Publishing, Atglen, PA 1998
I find no reference for a Me 262 A-1a/R1