With this bracket you can mount two cameras or scopes side-by-side. The bolts are standard 1/4-20 threaded as is the hole for mounting to the tripod. The maximum spacing is 9-1/2" on centers and the minimum spacing is 4" on centers. There is a rubber gasket covering the top of the bracket. There is also a wheel for putting the bracket on and taking it off the tripod so you don't have to spin the whole bracket around in circles. This bracket is VERY heavy duty. It is 11-1/2" long, cast metal, and the hardware appears to be stainless steel. This is a top quality product in very good condition. I got this as part of another deal and have not used it so I'm unsure about the details on exactly how it works, etc.
B & H Photo Video sells the new version of this item for $189.95. I'll take $100 plus shipping OBO. I will accept Paypal, Visa, MC, Amex, or Postal Money Order for immediate shipment or personal check if you are willing to wait 7-10 days for the check to clear.
See photos below. Thanks for looking.