IRON MAIDEN Monsters Of Rock 1980s prismatic pin

IRON MAIDEN Monsters Of Rock prismatic pin (1980s).
This one is a bit of a mystery: Maiden didn't play Monsters Of Rock before 1988, yet the pin itself definitely looks early 80s to me. It's Eddie first album's head featured here, and the badge was part of a very consistent early 80s collection (around 1980-1983). There's a smilar pin of Black Sabbath that I know of, probably made by the same manufacturer at the same period: https://i.etsystatic.com/10881518/c/1216/966/519/935/il/c4430c/272713298... - and as it happens, Black Sabbath didn't play MoR until 1992... Were they randomly made bootlegs not taking into account the bands actually playing the festival in the early 80s? Or were the said bands considered to play the fest at some point, but were cancelled after the pins were produced? Any insight about this welcome.

Very good condition - just slight rust stains on the back as per pictures.
Dimensions: W 2,9 cm x H 2 cm.