Bernie Wrightson credit in Overstreet and Incomplete Bernie Wrightson Checklist, confirmed by Wrightson himself.
Last previous appearance of Moon Knight was in Werewolf by Night (Marvel, 1972 series) #33 and next one is in Marvel Spotlight (Marvel, 1973 series) #28. The Moon Knight that appears here is a magical construct or clone created by the blood of Belaric Marcosa so it isn't strictly an appearance of the character. The same applies to Hangman and Doctor Glitternight.