Actually the Look Delta
are the oldest LOOK System i could buy in any shop.
None of the shop owners/employees knew any other older system before keo.
And the Deltas worked for all the old LOOK Pedals i had (i have 6 different old LOOK Pedals).
Took them for a tiny spin (~40km) and had no problems whatsoever.
Update: Got an E-Mail from a brand manager for LOOK who wrote:
keo cleats are NOT compatible with these old Look pedals. You will need the Look Delta cleats which are available either in black (no movement) or red (9° movement). [..]