A large segment of Area C (rear left) of the Firing Rooms was filled with data recorders, which used mechanical pens to plot changes in critical readings onto rolls of paper. 

These data recorders were all photographed in the Apollo 8 Firing Room Exhibit at the KSC Saturn V Visitors Center. I have been unable to identify any of these in period photographs of the Firing Rooms, so I cannot confirm that they are actual Firing Room equipment.  Their equipment tags indicate that at least some of them may be from the Army Ballistic Missile Agency (ABMA).  They may also have been installed in the Operations and Checkout (O&C) Building or at CCAFS.  There is not enough documentation to identify them at present.  However, the Dymo labels on many of the recorders are consistent with use in monitoring a Saturn launch vehicle and Apollo spacecraft.