I have a customer with good springs, but broken spring clips on each of the guide inserts. The one in the picture has a good spring clip, but a broken post that inserts into the guide insert located on each of the bottom corners. They are double hung, both upper and lower are active, but many have a broken spring clip. Can you decipher the correct part number? I seen one similar on the website, but it utilizes a coil spring. The pictures show the long spring type.
(Addition) Your part that looks similar is 15-251 (Inverted Universal Support) and 16-023 (Pan Am Tackout). The windows are older without tilt out option, though it can be tilted out by pushing out the left and right sides.
Sincerely, RS