Where Was the Photo for Simon and Garfunkel's Greatest Hits Taken?

We’ve handled a ton of copies of Simon & Garfunkel’s hits album over the years, but just lately we’ve started to obsess over the little golden knob that Paul Simon is holding on the front cover photo, so suggestively placed at groin level. What is it??? Is it some sort of Masonic or Rosicrucian symbol? Is it the compass from the dashboard of a Rolls Royce? Is it a trophy for selling a million copies of Bridge Over Troubled Water? Is it a solid gold pitch-pipe? Is it Art Garfunkel's immortal soul? Who knows????!!!! Fortunately, there are wise and industrious people in the world who do know, and furthermore, in an amazing feat of detective work, have tracked down the actual locations where the original New York City photos were taken for the front and back covers. Whew! What a relief! It’s a fence finial! 

(credit Bob Egan of popspotsnyc)