This spring broke and we have to keep the window locked in order to stop it from falling down. I can not find any marking on it to determine the weight of the spring.
Casey from SWISCO responded:
September 13, 2019
Hello,
I can't be sure since the parts are still installed in the window but you might need our 15-192 pivot shoe that works with our Series 170 and Series 171 coil springs. Thank you!