I used to have them on a Sintesi frame I had many moons ago, they give you the option of doing a full run of outer cable to the rear mech or running shorter bits with end stops, that one looks like it was knocked up on a lathe by someone... looks like brass ?
well, thats actually a cable stop yoke from an ancient proflex beast !! you should be able to get a plastic yoke to do the same job..i put that on the cove cause it was shiny !!
i also used to have them on an old sintesi moab frame, i think i still have them if you want any. they're aluminium ones, near exact same as in that picture. Let me know if you want them and i'll have a root for them.