A home owner from Potomac, MD says:
April 6, 2014
This is a broken part of a corner key for my screen frames I will need 16 of these and some new knife latches. These screens are about 20 years old and most of the keys have broken in half. The one in the picture is the best specimen I could get. I hope this helps. It is 3/8".
Paul from SWISCO responded:
April 7, 2014
Thanks for posting, Tony. Carefully compare our 95-181 to your hardware and see if this is a possible match.