Hi Manuel,
Eek! Putting your thumb through the ring leaves the knuckles open to contact with your opponents sword blade and you`re also more likely to break your own thumb!
Looking closer at the blade, I also have a couple more observations.
Look closely at the correspondence between the drilled holes and the fullers. All original C17th pierced blades that I have seen have the drilled shapes crafted in the middle of each fuller, as this process is done after the blade has been forged to shape and fullered, and before hardening and tempering.
It also ensures that the blademaker places his specific drilled and filed detail exactly where he wants it.
In the case of this dagger, several of the holes on the ring side flat of the blade are not so central to the fullers and in some cases almost half on-half off the fuller and rising ribs.
My first thought was that this may have been drilled and ground to shape by stock removal rather than being hand forged, which would indicate a much more modern manufacturing method, but the other side of the blade (thumb flat side) suggests that the drill holes have all been executed from that side, with all holes centrally marked and drilled according to these fullers.
The fullers on the ring side of the blade are not exactly aligned to those on the thumb flat side, which has resulted in the ring side drill holes being off-centre in several cases.
This is no indication of modern manufacturing method, simply mis-aligned fullering, which is common to historical European blades of munition - medium grade.
Something else that caught my attention was what appeared to be a couple of tiny highlights just to either side of the 3rd set of drilled holes in the middle fullers (ring side in your first pic) that looks like modern welding spatter
There also appears to be something that could be the same in the second to left fuller (ring side flat), just below the quillions. For the sake of your blade being authentic, I can only hope that this is not the case and that it is simply the way that detail is showing via the medium of e-mailed photographs!
The close up reveals good detail on the quillions, which would suggest that they are either forge welded and filed into form or cast, but being original and good quality in either case.
I hope that the above might be helpful.
All the best,
Macdonald