From The Estonian Philatelist site www.efur.se one can read about "Some of the rarities in Estonian philately" (Summary
of an article by Vambola Hurt in Eesti Filatelist #24-25, 1979)
Issue 2 1/2 Mk.
It is today practically impossible to find any item of this stamp
printed on horizontally ribbed paper, specially in mint condition.
It is known to exist only in very few collections.
Possible the date of publishing got something to do with the fact that the price does not reflect in the handbook issued later by Hurt and Ojaste.
Still the question remains for me - how scarce it is today, in mint and used condition?