1918 Deere

It sounds to me as though you may have an IH Mogul if it has only one cylinder; the Lanz Bulldog didn't come along 'til much later and was built in Europe. The current owner might also be mistaken in it being a diesel if it burns distillate or kerosene, which most all tractors did back then, though there *were* diesel engines as early as '18, mostly in stationary use. Remember, though, that Deere has been accused of "Putting the hit-and-miss engine on wheels" which is as much of an accurate description as it is a chuckle. People look at my 50 and becaseu they can only see one spark plug they think it only has one cylinder. your friend's tractor may have two and he doesn't know it.

Whatever it is, take it and bless the man that gives it to you.

I don't know if this will shed any light on your question or not, but this is some information I found recently that was an answer to the question "What was the first John Deere Tractor"?
Here goes:
"That question has THREE possible answers! In 1912, Deere & Co. began to develop prototypes for their own tractor. The only one that ever went into production (in 1918) is now known as the "Dain" tractor. It is named after Joseph Dain, the engineer who designed it. Only 50 to 100 or so "Dain" tractors were built and sold, BECAUSE.... That same year the Deere Company bought the Waterloo Engine Company, in order to obtain a factory in which to build tractors. The Waterloo Engine Company was already manufacturing the Waterloo Boy tractor that it had introduced in 1913. The "Dain" project was halted for two reasons: Joseph Dain had died, and the Waterloo Boy tractor was less expensive to build than the "Dain". Deere & Co. elected to continue manufacturing the Waterloo Boy tractors until 1924. This gave them plenty of time to develop a completely NEW tractor of their own. It was called the Model D. and it was introduced in late 1923 as a 1924 Model."
Sounds like your old friend may be giving you a pretty valuable piece of equipment!
gary