Winchester Systems Inc.

Any device whose MAC address begins with 00:21:3A has a network interface built by Winchester Systems Inc.. This prefix (the OUI, or Organizationally Unique Identifier) is assigned by the IEEE and is the first three octets of the address.

OUI prefix

00:21:3A

Organization

Winchester Systems Inc.

Address

101 Billerica Avenue Billerica, MA US 01862

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.