'Columbus' was the 'house brand' of the Radio Corporation of New Zealand Limited- a New Zealand company. Just as radio travels over waves so did the company's logo. Signs like this one would have been displayed by all retailers of Columbus radios. This radio range was sold from 1937 until 1961.
Radio Corporation of New Zealand Limited also founded TANZA- New Zealand's very first local record label in 1949. In fact, New Zealand made radios were popular right up until the late 1980s. But Columbus had set sail over the horizon by then.
You can see this sign in person at MAVtech- a technology museum located in Foxton's Coronation Hall. You'll also see lots of Columbus radios as well!