No idea what the record is, but the earliest any of ours have ever laid was some little speckled bantams we had once started laying a few very small eggs at around 4 1/2 months. Mostly I raise large breeds now and they start laying at anywhere from 5 to 8 months of age.
I agree but my Golden Comets started at 18-21 weeks (approx) and continue to lay 33 eggs per week (slightly less in the winter of course) after three years. The even more amazing thing is that Sex-Link Chickens produce a LARGE egg, not a medium egg like most production breeds. The Golden Comets I have are the best investment I ever made.