Second Rule LLC

Any device whose MAC address begins with 00:12:3C has a network interface built by Second Rule LLC. This prefix (the OUI, or Organizationally Unique Identifier) is assigned by the IEEE and is the first three octets of the address.

OUI prefix

00:12:3C

Organization

Second Rule LLC

Address

4119 Walnut Street Philadelphia PA US 19104

Source

IEEE OUI registry

Have a full MAC address? Look it up— we'll also tell you if it's a randomized (private) address rather than a real manufacturer prefix.