In Depth Study:

PCGS Holder Evolution

PCGS 4 (1990-1995)

PCGS 4, introduced in January 1990, was no longer a slab within a slab.  It represented the migration to the plastic, stackable holder that exists today.  The size and shape have remained unchanged since the introduction of this holder.  PCGS is no longer raised on the reverse but it was added in the lower right corner of the slab.  The label was printed on green paper and die cut from this point forward (the perforations are no longer visible at the edge).  However, the pigments used to color the paper were very unstable and many have changed color over the years.  Most are a pale green or light yellow but many other colors are frequently seen from bright canary yellow to light blue or near white.  The print still appears to be from a dot matrix printer with large size numbers and letters.  The serial number begins even with or slightly left of the beginning of the bar code.