Darren, of course you're absolutely right! This isn't an excuse but the 212 was the nearest of these that I had to hand and the right end of the fascia, where the '212' legend is written, was so dusty from storage that I never thought to check what it actually was.
I have since found my 215, a different animal in many ways, and all of its buttons latch down, which is rather more relevant to this thread!
Sorry.
(And I now realise that I have four of these sets, including the 215! Oh dear, it's worse than I thought)!