I don't know if it's ever been mentioned before, but on the pre-production suit you can see a metal thing on Fett's horse girth. It's on his right side, and in the stand up you can see it clearly. In the pic below, it's barely visible as a glint of metal on the belt. I couldn't find any other pictures of it, but if you've got the stand up or other pictures at home with a higher resolution, you'll be able to see it better.
Has anybody mentioned this thing before?