Anderson Window Sash Support

Good day.  The strings on my Anderson double hung window have broken.  Looking for a replacement sash support.  I have some numbers on the part.  B7 419 5-88.  The 5-88 I assume is the date of manufacture since these windows were installed in the fall of 1988.  Yes, they are 37 years old and still working fine.  The other number stamped on the item is 1600-17.  The box that the cord rides up in is 7" x 3".  The window itself is 24" W x 33" L.  It is a double hung window for a bathroom.  I would include photos of the box that holds the cord but it is very difficult to read.  So, I hope you can help me with the information I have provided.  Please respond to marshman99@yahoo.com.  Thank you.  Regards,  Tony Schmitt

I am sorry.  The other number stamped on box is 11600-17, not 1600-17.  

Bob - Thanks for a prompt reply.  What a wonderful resource Swisco is.  I learned about you by googling how to replace the balance on YouTube which directed me to your website.  Only 1 side is broken, but I had planned to replace both anywat (and, of course, that is your online recommendation).  Thanks again.  Best regards,  Tony