What this means
The IEEE assigned the MA-M block EC5BCD0 to DONG GUAN YUNG FU ELECTRONICS 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 EC:5B:CD:0, it is DONG GUAN YUNG FU ELECTRONICS LTD. hardware.