Ecuador: Our Lady of Mercy

Ecuador issued this stamp in 1979/1980 as part of a set of 13 featuring the Basilica of Our Lady of Mercy in Quito. (The stamps include the year 1979, but my catalog says they were actually issued in July 1980. The Virgin of Mercy is patron for the armed forces of Ecuador, so the stamps mention that also. I have 10 of the stamps, including the airmails. There is a subset of three which are imperforate and larger in size. I have not yet been able to find them. The stamps feature various indoor and outdoor scenes of the facility. Each stamp includes verbiage which describes the image shown. The present stamp shows a balcony (tribuna) with the lower portion of the organ case. I have not been able to find anymore information about the organ, though I have made inquiries in South America.