Posted By:
RhysIt is pretty simple, either it says PL in typed or hand drawn script (etched into the photo negative) or it is a team designation which was a chnage from 1889 to 1890 which would positively identify the player as being a Players League card (like the previously mentioned Comiskey). 1890 Old Judges can usually be identified by their crappy paper quality but that alone is not going to hold water when dealing with a player who could be 1889 NL or 1890 PL card with no other designation. In these scenarios collectors usually assume the 1889 and hold no premium to it. So basically what Leon said is right, if it does not say PL or contain a player/team combo which absolutely makes it a Players League card, than it is not one.
Rhys