The first stamp seems to have no structure at all, but when you look better you see a faint diagonal structure but no watermark! Zárate paper without watermark?! Some might even say it was a "trama cerrada"!
The third stamp has a faint structure and no sign of a watermark! However, the paper structure is asymetrical hence this MUST be Zárate paper with watermark!!! And there is no sign of a RAYADO either!
The fourth stamp is similar to the 3rd one! It has a faint structure and no sign of a watermark! However, the paper structure is asymetrical hence this MUST be Zárate paper with watermark!!! And the paper structure is a mirror of that of the third stamp!
And there is some impression of a RAYADO - see the red lines!
Both the 3rd and 4th stamp have the extra thick a the right [top in the images] that goes with base 17 (B17)...