The ATGBICS part numbers with the -C suffix indicate that the part is a 100% compatible replacement for the original OEM specifications. For example, ATGBICS # T8-3200-C replaces the original OEM part number T8-3200. The -C suffix is added to ensure the part is fully compatible.
You may also find yourself wondering what the -AT suffix for this manufacturer’s products means, as in part number AOC-QSFP28-100G-15M-AT.
These products are built around ATGBICS’s universally coded MSA network transceivers, rather than a single supplier’s proprietary standard. You can find more information here: Universally Coded MSA Compliant Transceivers – ATGBICS