Here's the Rupert in question. What a dude! Eminently impressive.

https://en.wikipedia.org/wiki/Prince_Rupert_of_the_Rhine

When I saw the title "Rupert's Property", I immediately thought of Rupert's Land which used to exist in Canada[0] (a large area around Hudson Bay, essentially). And as it turns out, it's the same guy! So apparently Canada also can be said to have Rupert's Property ;)

[0] https://en.wikipedia.org/wiki/Rupert%27s_Land

He is also known from prince Rupert's drops.

https://en.wikipedia.org/wiki/Prince_Rupert%27s_drop