Zerostart 3100003 is the OEM block heater that JD sells as their number AR87167, and typically has been about $87 from JD. AR87167 comes with a 1 foot cord, Zerostart comes with a 5 foot cord. The Zerostart heater has been running about $47-50 at Amazon since late summer 2018.
I just checked Amazon, they have the Zerostart 3100003 for $39.94 at the moment. For those that are needing/wanting to add a block heater to their tractor, now would be a good time to snag the Zerostart from Amazon. Get ready for winter early ! Don't forget, some applications will also require an adapter from JD to get the heater installed.
Amazon link: https://smile.amazon.com/gp/offer-li...&condition=new
Also a link to a GTT thread for helpful info for the 1 series (post #4) : 1023E, 1025R 1026R Aftermarket Parts, Cross Reference, Obscure PN