I've searched the Internet to include the Swisco part pages and am unable to find the two pieces in the attached photo. The storm windows on my house may be original to the 1973 house and one metal latch and many plastic tabs have broken.
The plastic tabs are about 1" long. An intact one is shown at the bottom left of the photo with many broken ones also shown. Most often, the plastic tab that keeps the window in the frame groove is broken. Also, the spring-loaded metal latch, marked "474", has a broken tab which also goes in the frame groove to hold the window in place. The 474 part mates with the 473 part (also shown) with one going on each side of each window allowing it to be raised and held in place at various heights by allowing the springs to push the tabs into notches in the frame.
Do you have the plastic tabs and the metal latch?
Thanks for your time! -Ken