Observatorio Naval Buenos Aires :

 

a clear morse code identification of the naval observatory (Willi Passmann)

 

Maarten van Delft received this QSL in 1965, an took a picture of the Naval Observatory later in 1973
here the QSL folder (Hans-Friedrich Dumrese, 1974)
this is a special edition for the observatory's 100th birthday in 1981 (Tom Rösner)

 

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Callsigns:
LOL

 

Frequencies Voice: & Telegraphy
5000
10000
15000