What this means
The IEEE assigned the MA-M block 7C45F91 to Hunan Shengyun Photoelectric Technology Co., LTD. Every network interface they manufacture under this block has a MAC address beginning with these digits, followed by a unique per-device identifier. If a device on your network shows a MAC starting 7C:45:F9:1, it is Hunan Shengyun Photoelectric Technology Co., LTD hardware.