I've found this photo of an original prop mask worn by the character Carl Franklin (played by Michael Burns, see below) and used in the episode "Fembots in Las Vegas, Part 2" (Airdate: October 1, 1977), it's quite obvious that the guys at the BSG prop department simply reused it for the Civilians in "The Living Legend, Part 2". They haven't even changed the color for the faceplate! Another hint that the Civilians were rather rushed together to expand the Cylons' ranks without spending too much money on expensive costumes like the Centurions.
In return, they used a slightly altered Fembot mask in Dr. Wilker's android lab in "War of the Gods, Part 1", seen very briefly at the beginning of the scene:
