I have a boxed MA77 myself. Found a picture (not mine) in the gallery,
your arm certainly looks quite similar, more complex counter-weight arrangement, with lateral balance perhaps? It has the black fixed curser and little red dot for vta/levelling as per the 77 though. Sorry, but can't supply any more info or a model number.
I've never got round to using the MA77, sits in it's box, just waiting.
Does anyone know anything about these. Are they any good?