who knows what this is?

[Olive Drab]

Stopped by my sisters today and the brother-in-law says "Hey jas what's this" ummmm I dont know says I. But i bet I know where to find out.
The info from the guy who sold him the car is
Its a diff lock turn the little thingy then turn the big thingy etc. Also told it has Mcfarlane axles ???????
Questions 3 i have for thee
1. What is it ?
2. Who is mcfarlane and why is he special?
3. is it worth keeping on the car or will this be a disaster offroad?
thanks in advance AGAIN

[slug_burner]

I suspect that it is a McNamara diff lock and axles.

should work ok just have to get out of the car to engage and disengage.

[Olive Drab]

A further question if i may. It is mounted to a rover diff, my bro-in-law has come from the darkside (Toyota) to a series Just wondering if he will be likely to brake both axles at once with this engaged or will this decrease the likelyhood of axle sagas. i only ask because i think he suspects he can be as nasty to a series2a as he was to his previous 60 series yota.