'A' stands for 'Atrappe', literally "Mock-up'. The camera (or at least the top plate) is from a non-working mock up M2.
So the questions;
Is it working? In which case the top plate has been taken from an Atrappe model and fitted with working innards. The collector value is unsure, it's not original but it is a curiosity.
Is it not working? In which case it is likely original and has some collector value, but of course no real camera value - it doesn't work.
Would I buy it? Not at a large premium (maybe at a small premium because it's kinda cool).