During my stay on a campsite in the north of the Netherlands I enjoyed good conditions on 12 MHz in a relatively noise free environment. That resulted in the reception of a lot of new DSC stations. SHN (Servicio de Hidrografia Naval) in Buenos Aires, Argentina, was one of those!

QSL Servicio Hidrografia Naval Buenos Aires
QSL… just three letters, but I got my QSL for MRCC Buenos Aires!

The email reply took hours only and was the shortest possible. But it carried the three key letters: “QSL”! (I added their logo to the email myself to improve the appearance of this post).
I sent my report to shn@hidro.gov.ar. Confirmation followed via snautica@hidro.gov.ar, which is probably the Coast Guard branch.