The Grateful Dead: spot the difference

Here's a surreal flashback to those prehistoric days when teenzines featured people who actually wrote songs and played instruments. It's from the October 1967 issue of 16 magazine (described by the late, great Derek Taylor in Fifty Years Adrift as 'the single most popular and powerful fan-magazine in the world'). Other bands that featured in its '5 Errors Contest' included HP Lovecraft, The Youngbloods, The Electric Flag, Canned Heat, The Yellow Payges, The International Submarine Band and The Mothers Of Invention.

By the way, I can only see three 'errors' here:

1) there's a button missing from Bill Kreutzman's jacket (second left)
2) the gem's missing from Bob Weir's necklace (second right)
3) the keys around Pigpen's midriff have vanished (far right)

I scent a stitch-up.