25 de Mayo was overhauled in the 1980's and received Decca RM1226, and MM/SPN-720 radars.

The modern 720 looks different. https://www.radartutorial.eu/19.kartei/03.atc/karte078.en.html

Photos of Karel Doorman in the 60's and De Mayo in the 70's to 90 show this CCA radar always installed, so it wasn't new in the 80's.

Early Decca radars had similar shaped antenna, but I can only find pics of models, or airfield antenna.

The only other antenna that looks similar is the Scanter 4100
https://www.radartutorial.eu/19.kartei/03.atc/karte052.en.html
However, I can only find newer photos, so don't know if it was around in the 60's.

The 91 edition of the worlds weapons has a photo of the 720 that's supposed to be on De Mayo, but it doesn't look like the radar in the ship pictures.

60's editions of Janes don't list radars. 80's edition lists the 720.

This is a composition of photos of the radar over the years and what the 720 is supposed to look like.



The only thing I can think of is that they used the old antenna with newer electronics. Not unheard of, but not common practice.

Interesting puzzle.