I found just now a wonderful example that was generously posted by Mahratt on a Russian forum : a 3-D photograph of a dagger from one of the Russian museums. It is defined as Zirah Bouk by the museum and Mahratt did not cast any doubt on this attribution.
Here it is:
https://forum.guns.ru/forummessage/79/2328051.html
The beauty of it is that we can rotate it any way we wish. It is as close to " I hold it in my hands" as possible.
The distal half of the blade is diamond-shaped and just a tad thicker than the flat part of the blade, no different than Artzi's example and the one presented by Rumpel9.
Citing Stone: "A knife with a point thickened so that it is strong enough to be forced through mail. The name is given to any knife with the point reinforced"
Citing Elgood: " Dagger with a thickened point to pierce mail"
I might have contributed to the confusion of this discussion by using word
" massive" in reference to the reinforced part. Sorry for that. The degree of thickening could vary just to assure sufficient mechanical strenghtening, and a conversion from flat to diamond-shaped with even minor thickening is mechanically enough to create a stiffening rib and prevent lateral bending.
Thus, Runpel9's example is a Zirah Bouk.