Wavechickens
Chirping
Ya the earliest I have ever read about is 4/4.5 months and they are always producing birds. Lay ealry and often, like Rhode Island Reds, sex link (golden comet or black sex link), and leghorns. I don't know if there are any that lay earlier. I know production birds are highly valued for that reason when choosing your breed, now if only the multi colored layers were like that. My parents big light blue layer (Easter Egger) took almost 10 months before she layed her first egg, and lays twice a week if we're lucky. Her counter parts (another Easter Egger who laid small light green eggs, two Rhode Island's, and three Australops) all started between 4-6 months!