Ok technically the Leon Day isn't his rookie card. But since he never signed any of his Latin American cards, this is really your only option as his earliest possible signed card.
The 1978 Long Ago Black Stars cards are 3x as scarce as the Old Time Black Stars cards. Only one Leon Day example has been encapsulated by PSA/DNA.
Cool Papa Bell Rookie Card $200
Leon Day First Signed Card $200
Jimmie Crutchfield $40
Joe Greene $40
Pat Patterson $40
All prices delivered.
Tom C