PJ5FN 1949 Aruba, Netherlands Antilles

Printed on the card: QSL UNDER COVER ONLY.

As far as I can establish, Joaquin M. Kelkboom was QRV as PJ5FN 1949-1952 and then got a resident's call - PJ2AD.

QSL from the estate of W3EVW
Info courtesy of 5B4AHJ