NS-10M PRO (aka NS-10M Professional, NS-10MP): This model is the most similar in appearance to its predecessor, the original 1978 NS-10M, because it stands up vertical and has a removable front cover (black or gray). The obvious visual differences it has with the original are: the name label next to the tweeter (which tells you clearly it’s an NS-10M PRO), the new tweeter design & poking-out grill, the new terminals on the back, and the absence of the black & white, detailed specs sheet on the back.
NS-10M STUDIO (aka NS-10MS, NS10MS, ns10s, ns-10s, NS10’s, NS-10M’s etc.): One of only two NS10 models that sits horizontally (the other is the MC). The name label is also turned 90 degrees, accordingly, and states clearly that it is an NS-10M STUDIO (all capitals) model. It is the only NS10 that has no front cover option, and thus no holes for the cover to clip into.
NOTE: If the speaker you’re looking at is not designed to sit horizontally, then it is not an NS-10M STUDIO. Many people selling the original, older, vertical NS-10M falsely claim that their speaker is an “ns10 studio” model, which causes lots of confusion.
NS-10MC (aka NS-10M Consumer, Commercial): The same as the STUDIO model except that it’s designed to be suspended or mounted, and thus has holes for this. It is one of only two models that sits horizontally (the other is the STUDIO) and it's name label is turned 90 degrees to accomodate this. Unlike the STUDIO model, it has the option of a removable cover. It can be suspended via the Yamaha BWS50 260 Wall Mount Bracket.
NOTE: I’m not sure whether any adjustments were made to the NS-10MC to compensate for the lack of boundary reinforcement that would/could come from being mounted, rather than sitting on a mixing desk or bookshelf. If you have any info on this, please contact me, I’d love to know.