My guess would be one of the "improved" breeds.

Maybe RI Reds, or NH Reds? I'd also guess it's NOT one of the heritage breeds.

As far as I know most chickens only lay well for about 3 years, then start slowing down in production.

Brendasue

Most do slow down, but the upside on my older hens are eggs so large, even the cartons designed for jumbo eggs won't close. I think Brendasue has it, in that your hybrid breeds seem to keep cranking.....those who are fantastic layers in their youth. My older hens are golden comets a hybrid off Rhode Island Reds......who really are an old breed but so prolific that they are seldom called heritage. I know I have a few up there so old that I've been teased of running an avian geriatric facility. I brought new blood in this year and the ones who are past three are going to be going bye-bye. I don't like butchering but I think that is their fate for broths.

Thank you. I know a little.