The full name of the lens is Leica Tri-Elmar-M 28-35-50mm and it was released back in 1998. What is special about the lens, is that they are aspherical (a lens whose surface profiles are not portions of a sphere or cylinder). They were only produced for 9 years, from 1998 through 2007, due to the incredibly complicated design and expensive manufacture of it. You can still buy used lens on Ebay, but, as you can guess, the price of it is quite steep.