Per your request, I have attached 5 photos showing the shoe removed from the window track. (Note that this is not the part that needs to be replaced.)
All photos show the track removed from the jamb and one of the shoes removed from the track. The other shoe can be seen in its normal position. Note that the shoes are handed. They are 1 1/8 inch long. I don't see any numbers or letters stamped on the casting.
Please let me know it you need any more info.
Don
The shoe attached to the counterbalance spring. The spring and shoe at the bottom are lying just above their normal position (out of the plane of the photo). The shoe in the other track above is in its normal position. It is cocked, locking it in place when the sash was removed. When the sash for the upper show is replaced, it pulls the shoe down (in the photo), pulling it away from the side of the track and unlocking it.
Same as above but shoe and spring displaced for clarity.
Shoe disengaged from spring.
Shoe turned over. Looking at the side normally closest to the jamb.
A rotation of the above view. Again, the side shown is normally against the jamb
Here is one more photo: an end view of the balance track
