Can they be dated?
They can be dated --- sort of. Since there were so many makers over such a long period of time, they become difficult to date.
You need to look at charts of French military proofs. That gives you a range: "Used from 1809 until 1812" as an example.
Then compare proofs that may come from the sword being re-issued, "Used from 1810 until 1820" as an example.
That will give you a range. I am no expert at it, especially the French ones. I would date my sword between 1810 and 1816.
I don't think that there is a complete list of proof marks to be found --- anywhere. Here are some hints that I used:
1) German state manufacturers usually can be dated by when that state was under French control.
2) Spanish manufacturers generally put a date on the blade.
3) French manufacturers sometimes dated the hilt, but mostly used proof marks.
4) Eastern European states --- it's anybody's guess --- best bet is to determine when the state was held or allied to the French.
It gets even more complicated when you consider that many European countries put these swords into service for their own military after the Napoleonic Wars were over.
I recently saw one of these swords for sale as "A 100% original sword from the Napoleonic Wars", guaranteed original, etc, etc. The sword was a Spanish manufacture and the blade was dated "1856". Napoleon died in 1821.
What can I say, Good Luck.