A quick learner from Bethlehem PA says:
August 29, 2016
The windows have no brand names or numbers on them. As you can see the end of the tabs have broken off and the window no longer stay up. The broken part which is spring loaded fits inside the corner piece. The stationary corner piece is 1 1/2 by 1 7/8. The broken piece is 2 1/2 w/o the broken tab piece at the end. Do you have a replacement part for this window? I actually need to repair several windows with the same problem.
Tom from SWISCO responded:
August 31, 2016
We may have something that can replace this, but I can't be sure what you have based on these pictures. Is there any way you can show me one that hasn't broken? The style of the tip is an important detail. Thanks!