This ships inside of numerous notebooks, including the Dell Latitude E6510 and family. No current free software firmware exists.
LSPCI output:
Slot: 03:00.0
Class: Network controller [0280]
Vendor: Intel Corporation [8086]
Device: Centrino Ultimate-N 6300 [422b]
SVendor: Intel Corporation [8086]
SDevice: Centrino Ultimate-N 6300 3x3 AGN [1121]
Rev: 35
03:00.0 Network controller [0280]: Intel Corporation Centrino Ultimate-N 6300 [8086:422b] (rev 35)
Subsystem: Intel Corporation Centrino Ultimate-N 6300 3x3 AGN [8086:1121]
Kernel modules: iwlagn