Overhead crane pulley

1917 was a great year for overhead crane pulleys as I'm sure you know. Powered by human muscle using chains or ropes, these iron gantries allowed heavy items to be moved around in stores and workshops before decent electrical motors and reliable hydraulics were developed. I stumbled on this obviously removed and restored piece standing outside in the boatyard in South Queensferry. Most likely an ex-MoD machine rescued from the remains of the old Naval Yard that closed down in the late seventies. With a SWL of only 2 tons and a test load of 3 it's not exactly a heavy metal beast but it's nice to see it remaining in good condition. The question is where on earth and in what building and with what supports would it ever be set up and run?