Any info on what the bracket might be for? I thought the obvious one would be licence plate but having looked through hundreds on ebay I can't find anything that would fit, mainly because the fixing point is between the rails. It had four raised spots which may be made to fit to something with four dimples but I couldn't find any reflectors like that.
These Troxels were made by Middlemore, they are rebranded B89 saddles.
I had one like this with a reflector on that tab. I removed the reflector at one point. The backing plate was aluminum and had the dimples, but the dimples appeared to have been caused by the raised points, not by a manufacturing process. My guess is that the raised points exist to lock the reflector in place as it is tightened down. But then again, someone could have added the reflector themselves