1997-2003 era Shimano XT and XTR v-brakes with the parallelogram design. Aside from not requiring pad realignment as the pads wear thinner, these brakes are also shaped for slightly greater mechanical advantage compared to typical v-brakes. The side effect of this is that their pad movement is very small, so your rims will have to be perfectly true. They also have a reputation for squeaking.

I run these brakes on our two touring bikes. Quite hard to find nowadays and very expensive on eBay. I have an extra set stored away for my own future use.