My guess is that pipe cap was made by Grinnell. They had a foundry near here some years ago.
Sounds like a great outcome!My property line story:
When we bought our place our neighbor was at one time the original owner of our land, and he had a super wide easement across our property. The easement amounted to over an acre and cut right through the middle of the property.
I'll spare you all the details (long and drawn out) of issues with the old neighbor, but he passed and the family sold the property to a company.
The company has been the greatest neighbors anyone could ask for.
Turns out the Old man had moved every single property corner 30+ feet in his favor many many years ago around 1940.
He used a very old Idaho farming law (1840 iirc) that said that any farm owner could use 30 feet of any adjoining property to turn mule teams around, and used that to justify his "taking".
Well it's not an active law and the new owners got enough complaints and inquires about "real property corners" that they did a full survey, I offered to pay for my line but they said it was no problem they would pay for it.
Turns out they lost 24 acres in total on all the property lines, I gained 1 1/4 acres out of it.
Oh and they didn't want or need the easement across my property and "sold" it back to me for a really good "price".
So I have great neighbors, with Zero issues and no more easement across my property and gained 2 1/4 acres.