I always check eBay for completed auctions to see what they went for. You can usually get a pretty good idea from 5-10 auctions what people are willing to spend. However, in your case I didn't find any completed ones and only 1 active listing
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. As of right now it's down to 6 hours left and no bids at $10. Who knows if there will be a last minute flurry of bids, but usually if there is interest at that price at least one person will have bid by now. So, my completely layman's estimate is $5-15.
I have about 20 braces and I don't think I paid more than $5 for any of the braces. Before you ask I thought they'd look cool hanging on the wall along with the approx 75 planes, 20 scribes, 10 folding rulers, 5 bow saws,
20 squares, etc (I need a life or at least a bigger shop).