The "C" indicates small format IC core, which is the only core style Falcon products. The C987 will be provided less core unless -6, or -7 suffix is specified (6 or 7 pin core)
Example:...
Unless otherwise specified on an order, the cam supplied on Falcon mortise cylinders will be the following:
Non-IC mortise cylinder is the 5622-STD.
IC mortise cylinder is the 5622-IC.
Related...
Cams for other applications may be specified with no additional charge, see pricebook.