I am afraid it is not er16. maxnc actually just used the core of a taig lathe spindle iirc - they used to claim they were some special proprietary thing they built on their own, but they would actually apparently just buy lathe spindle rebuild kits from taig and repackage them into their own head clamp. this meant they used taigs old collet style, not the er16 style. so this makes things really easy if you just need replacement collets, as taig still sells those type.
this also might actually make things easy for you if you do want to go to er16, as you could look into getting a taig er16 rebuild kit and collet set and seeing if you could simply swap the spindle core that is in there. just a guess, but its very likely pretty much a straight swap more or less.
this would likely be a pretty easy way to get the er16 collets, but at the same time i am hesitant to say if the lesser runout of the er16 would solve any problem you might be having though; from my experience the maxnc10 was not a very rigid machine and tended to have a lot of flex and deflection under load, which may be where any tool breakage, dulling, or chatter you experience may come from, something not necessarily fixed by a more accurate collet type.