Vintage Singer 27 / 127 / 128 sewing machine feed dog. Various styles of feed dogs were used on VS machines, this is part #8213 (please compare with your existing feeder) which is compatible with the #8240 throat plate. Very good vintage condition, may have typical discoloration consistent with age but will be clean and rust free. Comes with mounting screw. Original, genuine Simanco part.
Usually ships within 3 days. 
