Brothers from a different bladesmith - Two quite similar small swords

[Triarii]

I'd agree on the features, especially the bivalve one, being C17th. The work on the quillon block on the bivalve one is quite crude though, in form and finish. Replacement?

[urbanspaceman]

I acquired an interesting variation on this theme some years ago (picture forthcoming) and was led to believe it was a Dutch ambidextrous dueling sword.
There is a series of Xs on each side of the blade at the forte.
It was dated, by the vendor, to the end of the 1600s.
It was considered a transitional rapier - which seems questionable.
I have subsequently seen one more with a completely different blade (see final pic) and now yet another two.
I think the hilt is the defining identity and look for confirmation as to its origin.