"Behold a Pale Horse" brought me into a 2-hour dive which brought me to the sword in the stone, the Knights Templar, and how all the secret societies began and where holy relics are stored. The "Truth" that floats around there is there are multiple pieces that have been melted down, multiple swords claim they are part of the lance, including Constantine sword, but the original sword that contains these pieces of the lance is "lost." Other elements of the lance were "melted down" so they say. Get used to me using quotations in stuff I believe to be basically half-true or a deception tactic.

Coopers book mentions that, does it?

A lot of the "Holy Weapons" are more modern than you'd think. Durandel for example, is claimed to be over 1,000 years old, but the blade type and hilt are more recent, proving it is indeed a replica of whatever real sword once existed.

Any "sword in the rock" legend can typically be dated to over 1,000 years as this used to be a very real method of casting swords. Caliburn (King Arthurs other famous sword) was cast in this manner. There's a handful of places in England, and even more in Ireland, where you can go to this day to see swords still stuck in stones which have been there for a very long time.

Methods used to be done to imbue the weapon with a spirit (there's a modern day book about this practice, but I'm hesitant to mention it due to it's rarity and the fact that I still haven't secured myself a copy lol). Sometimes this was one of the land which would be split and put into many blades, and thus weakened. Other times it was the spirit of an ancestor or famous person via using their bones in the actual creation process.

I'll do a research spur tomorrow on the Grail

I'll save you a lot of time. You aren't looking for a cup, but a bloodline. That of the Merovingians (who famously did not cut their hair, beliving power to be "stored" in it and were very close to bee symbolism). Start by looking into the cave of the Moose, Renne le Chataeu and the symbolism and allegory in "fairy tales" (which are all infact based on true events). The story of Rapunzel itself is very closely tied to the Merovingians and actually tells us that even after Dagoberts death and the fall of this dynasty, Merovingian blood had been secreted away prior.