The Postaco stamp issue of 1915 was once considered unbelievably rare until a small find of complete sheets in the mid 90s increased the population of this interesting set, and made them easier to collect - though still rare.  This example was probably not from that mid-90s find, graded GOOD 2 by PSA due to soiling and likely use, along with some irregularities around the perforated edges.  Despite the technical grade, the black and yellow coloration makes this stamp bold and vivid.