Yes I did and liked it very much although I only put a couple of films and didn't get anything I thought was noteworthy. Keen to use the Mamiya again for something (not sure what yet) unless you need it back?
It refers to the colour of the centre of the shutter cocking lever. Later shutters had the blue dot and so it is often taken to refer to a later lens and hence a more modern coating. Another piece of lore for these cameras / lenses is that the earlier lenses were 'sharper' than the later ones. They were used for portraiture and weddings and often photographers fitted soft effect filters to create more flattering images. I have heard it rumoured that Mamiya responded to this with the later lenses.