From what I understand, these were supposed to go on a Harley-Davidson 883, but I can't find an example of that online. Got them with a bunch of 883 parts. They are still in the bag and have two posts and have two lock ring washers that hold it on. They are 4" long and 1.1/4" inch wide. The posts are approximately 2.3/4 apart from post center to center.
They are brand new, still in the bags.