Ooh, oww, ouch.... That's a bit like saying it's okay to make coffee tables, bookcases and fishtanks out vintage tellies!. There are some "out there" who collect and restore vintage cine cameras and projection equipment, in much the same way we collect radio, audio and TV equipment.
However, I can see now why these amps have a degree of desirability about them.. I'm surprised at 18W output, and in push-pull, and even more surprised that the amp's designers went to all that effort, only to limit the frequency response to little more than "telephone" quality (big telephone mark you, but telephone range of frequencies nonetheless).
It is my recollections of these projectors at school, and the weekend film shows at the village hall, that made me question their use in serious audio applications - purely because they never did sound "Hi-Fi" enough for anything else than a film about how tea is made, where rubber comes from, or a few Tom & Jerry cartoons on a Saturday morning.