Lawson Industries window balance rod.

Hi there, Greg.

We should be able to help with this. Can you show us clear and up-close photos of the top and bottom fittings? I will do my best to assist from there. 

Thank you very much! Either the S380-28 or S385-28 are my recommendations. The best match will depend on the depth of the bottom fitting as shown in the photo below. 

Your 2790 stamp is from an old rating system so it won't match any of our options. However, the "30" might indicate the sash weight. If that's the case, you can go with either the 2750 or 2760 stamp option. The 2750 option will carry a sash weighing 26 to 30 pounds and the 2760 option will carry a sash weighing 30 to 33 pounds. I recommend weighing the window on a scale to be safe. 

Let me know if you have any questions!

Comparison of the S378, S380 and S385 balance shoes.