Spring opener, balancer

Thanks for writing in. I'm confident we can replace this balance for you, but it will have to be custom made: your stamp code indicates that this is a 'dual-spring' balance, meant for an especially heavy window. I just need a little more information from your end to get this started for you. Can you provide the length of the metal channel, not including any fittings at either end? Finally, can you provide us the exact weight of the window sash? This information will help us get this started for you. Many thanks.