If the serial number indicates it was made in 1970, it's not multicoated. Schneider started multicoating their lenses in 1977, starting with the Symmar-S series. Multicoating of the f5.6 Super Angulon series began in the summer of 1978. If it's multicoated, it will say withe MC or Multicoating on the outside of the front barrel.
$540 would be a good price for a newer, multicoated sample in excellent condition. For an older, single coated sample, I think I'd pass at that price (or try to talk the seller down).
Kerry Thalmann
Really Big Cameras