The cannon pinion started slipping after a few days. It's tricky to tight one of this type. It's fragile for one thing, but also if it is too tight that inner ring engaged during setting will slip. There is a very narrow range of "snug-ness" that will work.
I always enjoy these late period, thin, 12 size Elgins. They are extremely well made. Everything goes together well. In many ways they represent a perfected product.
Elgin serial number 35535731 is a grade 315, 12 size, 15 jewels, made about 1935.