Two years ago, I wrote about the P-1956 mainspring from Merritt’s Antiques. This spring was ideal for many antique American clocks.
My newest batch of these mainsprings (received late in 2009) are weaker than the first batch I had. When removed from their clamp, they open out to only 5 1/2 inches (my first batch opened to about 11 inches).
These springs may be too weak for clocks with a recoil escapement. I still need to test them in a Seth Thomas No. 89 movement.
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