Hi
I see in the photo that your specimen has rounded edge ribs, and Helvella acetabulum has sharp edge ribs. I think your specimen is more like Helvella costifera.

Best,
Fidel

Well,
the first idea observing the photo is H. costifera, also because the ribs are whitish until their very end.
It's true that, usually, H. costifera has more rounded rigde edges.  But it should be said that the sharp ribs in H. acetabulum become evident when the ascomata are rather developed.
In our case, the very small ascomata and the spores at the lowest point of the usual range seem to indicate that the specimens are rather young. In the first stage the ribs are blunt and rounded also in H. acetabulum.
H. costifera, at least in my area of collection, is mostly gray rather than brown.
So I think we will keep some doubt about this collection.
Reza, what did you mean with "sharp edge ribs"? Because in your photo, as Fidel pointed out, the edges are rounded, not sharp. Maybe you mean that the ribs ends abruptly on the surface of the apothecium?
Regards
Mario