This casting had been on ebay for several weeks with no interest, and when I looked at the pictures, I noticed the scale in degrees. That got me thinking of what it could be turned into. The round part is 6" in diameter. The start price was low so it was cheap without any bidding competition. The degree scale does not go right round, it is 90 – 0 – 90 and the correct attitude would be with the square part at the top. Could it be from a small milling machine?