The Skeleton Warrior was released fairly late in the Fiend Factory range as FF52, possibly as Games Workshop still had ties to the Minifigs Valley of the Four Winds range. It was followed by the Skeleton Rider on Horse of Hell as FF66 in August 1980.
FF3-2 Wraith Rider on Undead Horse replaced the TSR licensed Hook Horror in Febuary 1982, and the Skeleton Warrior was remodelled in September 1982. It possible that the mount for FF66 was changed to one shown with the C21 version but I haven't seen any proof of that. It might also have been dropped from the range, it doesn't appear in the 1983 Citadel Minaitures US catalog, or in the 1983 Dragon catalogue.
The Wraith Collecting Souls was released as FF86 in the US but is shown as a Wraith Rider in the C21 Fantasy Cavalry range in Compendium One.
Sculptor:
The Perrys
Painter:
Orclord / Richard Facey / Richard Abbott
Source:
Orclord
Released:
1979-1982