The detachable faceplate for anti-theft reasons was (is?) a very common feature for aftermarket radios/head-units/whatever in the US. Built-in ones have just increasingly moved to not being a discrete, accessible, interchangeable component, another way around.

I still remember when my dad had bought an aftermarket tape-deck-only radio, a Sony I believe, well into the era of the ubiquitous CD player (he just wanted a working tape deck). Someone broke into the car at some point and stole it and I can only assume they were very disappointed after looking closer.