What this means

The IEEE assigned the MA-L block 00035F to Prüftechnik Condition Monitoring GmbH & Co. KG. 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 00:03:5F, it is Prüftechnik Condition Monitoring GmbH & Co. KG hardware.