Predecessor lettering on Conrail cars

Most Conrail freight cars out there have in the top right corner a stencil of what the cars former number is. I've noticed usually original owner. However tonight I had a covered hopper in my train the had the stencil up top that said PCB then the number. Anyone know what PCB stood for?

The PCB you saw is a Penn Central reprting mark for a group of 1,251 covered hopper cars PCB 888749-889999. There was/is also a group of boxcars with a PCA reporting mark. These were used instead of a plain PC for financial reasons.

the PCB marked cars were leased thru Pullman-Standard Company and were applied to Penn Central cars:
Covered Hoppers H54 Class cars 888749-889748 cars could be both found in both Green or Gray paint sceams.

the PCA Marks were applied to ACF Cars that were leased to Penn Central under numbers:
Class X71 Boxcars 166000-166999

info is on pages 37 and 105 in the book "Penn Central Color Guide to Freight and Passenger Equipment" : by James Kinkaid

FWIW, when no predecessor number is present the class designation is a clue - PC cars carried NYC or PC class designations, other roads got a C_-## where the blank is the first letter of the predecessor road - CE-16a is an ex-EL covered hopper, for instance.