I acquired three Look ascenders from Repetto Sport in 1982.
The Look is a semi-mechanical ascender that works on single or double rope. It consists of a single forged aluminum plate with several holes and notches. Four small holes admit the 6 mm. sling rope that was provided with the Look. The standing ropes fit into the large notches, and a bight of sling rope passes around the standing line and hooks into the small notches. The larger holes are nonfunctional.
The Look can be rigged in well under five seconds, if you know how. When I bought these, I bought a third one to offer Bob Thrun (of Prusiking fame) if he could rig it in less than two minutes. I made sure that there were enough witnesses to make him nervous enough to lose, then let him keep the ascender anyhow.
The Look holds well enough to use, and the large plate makes it easy to move - simply grasp the standing line and slings with an open fist below the plate, and push up.