Sergio,
all have orthogonal watermark and a symmetrical paper wire hence are all national paper, I can not say anything about the coatings....
The letters AЯ are indeed barely recognisable in the stamps you have indicated with ?? ; true, but nothing special for the national paper

! I should not be worried about it!
The 2 orientations are what counts most! The stamp with an a-symmetrical paper wire - see my earlier post - is the version that may be the imported paper in the 2p Sarmiento
Direction of paper vertical, parallel to the long side of the stamp "M"inverted AЯ [??]:
Direction of paper horizontal, parallel to the short side of the stamp "m":
AЯ with bottom facing the left [??} left stamp; bottom facing the right on the other [??].
Direction of paper vertical, parallel to the long side of the stamp "M"; inverted AЯ [??]:
