dungeons and dragons – What is the earliest example of a variant monster in a published D&D adventure?

The earliest published standalone adventure for Dungeons & Dragons was Palace of the Vampire Queen. That adventure has several variant monsters. In particular, the Dwarf Children all have 1 hp (technically 1 ‘Max. Damage’) (excepting the Princess, but she is labeled ‘dwarf princess’, not ‘dwarf children’), and none of them have levels in fighter, while the Dwarf entry in Monsters and Treasure allots 1 full hit die to each dwarf and instructs that one out of every 40 dwarves in any given group should always be a levelled fighting-man.

No specific published stats for dwarf children followed in any manual for the very early game (at least, not explicitly), and the children don’t receive full stat blocks, sort of, since if they get attacked or try and punch something you gotta refer to Monsters & Treasure again to find out they are extra good versus the Ogres on floor 5 room 13 and “otherwise as outlined in CHAINMAIL”.