Hi, the window is an Alside tilt window, where the bottom only tilts out. THe part doesn't have any numbers or anything on it. The only part that is broken is the pivot shoe. I think that what is called...the little cam thing the window slides into. The window is 23 1/2 x 59 1/2.
Tom from SWISCO responded:
September 15, 2016
Yep, pivot shoe is the right term! This appears to match our 15-177. Take a look and see what you think.