Definitely used to be a thing in New Zealand AM broadcast stations. For example, here's an old antenna sign: https://photos.app.goo.gl/tzbJYT3nGpHELPWk6

I think the FM callsigns for the same station were different (four characters rather than three), however could be related, but the callsigns were eventually dropped or incorporated into the station name as it stopped being a thing broadcast stations needed to announce (or maybe even have.) For example, as the station that had that antenna above started FM, it had a callsign but now it's just left in the name: https://en.wikipedia.org/wiki/ZM_Wellington