I had thought the saddles for these bridges were only nylon as well, but a little searching turned this up from the Two-Point Bass Bridge section at Fly Guitars http://www.flyguitars.com/gibson/bass/parts/bridge/2pointbridge.php: "In 1972 the saddles were upgraded to metal (image 5), shortly before this bridge was replaced by the three point."
Anyway, hopefully that means they are original.
My '72 EB-4L came with metal saddles, exactly like yours............ Long live the "Tilt-O-Matic" bridge!
