price? grade range? prefer PSA,SGC or Beckett?
Years? you say 50's ..i just bought a 48-49 Leaf RC, plus theres the 49 Bowman, or perhaps the 52 is suitable, its basically your choice what you like.
Once dteremined, then how about centering, creases, corner wear?
Here, click this site, to view many Jackie Robinson cards by year(s):
http://www.cardboardconnection.com/t...robinson-cards