Mercurio by Juan de Bologna, printed by the National Printing Press of Montevideo using the lithographic system on sheets of 100 stamps on thick paper with a perforation gauge of 11.5. This series of stamps was reprinted on watermarked paper in 1923.

However, these three stamps, in particular, belong to the varieties without perforations, which are described in the specialized catalog of Uruguay by Ciardi.

Are not rare but not usual to come across... lets say once each 2 or 3 years !