Misspelled it. Here's a quick tidbit I found.
http://www.mcnamaradiffs.com.au/company.html
Jack McNamara locking differential. This Australian-made unit can be powered by engine vacuum so it avoids the need for a compressor. Like the ARB, it utilizes a sliding collar arrangement but it is much larger and doesn't require any seals inside the differentials. Installation of this locking diff should be easier than an ARB. The McNamara differential has been on the Australian market for a while but as yet, there is no North American distributor. Current applications include Dana 60, Dana 70, and Land Cruiser and Toyota pick up axles.