Top of window stop

Hello there!

I'm afraid the part shown here is too obscured to identify. Can you remove it from the window and show us some photos? I will do my best to help from there. 

Thank you kindly! I recognize what you have here. This part is called a top sash guide and it appears the 18-124P is a good match. Look over the specifications and compare them with yours to see if they match what you're looking for.