Identify coil spring please

I think this might be a match for our Series 160 coil spring. There should be another number aside from "35" printed on the spring but I can't make it out in your photo. It may be too faded. Check the other springs in the window to see if you can make something out.

Well, what has me puzzled is that the window manufacturer only used two coil springs (one on each side) for a 25 pound sash. That would mean your springs are made to support 12.5 pounds each, which is exceptionally strong. We don't have any spring that large. If you are positive your sash is 25 pounds, I would recommend four S160-6 springs. Each of these can carry 6.5 pounds (26 pounds altogether, which we think should be okay), so you would use two on each side. I'd also recommend a double support like our 15-150D.