Hmmm ... interesting example of a lovely coin to evaluate.
First off I'll mention my personal bias against toning in this series ... means nothing relative to technical grade ... but I prefer my classic US silver commemorative to have minimal (or no) toning ... and the unusual blue/green stripe on the reverse is distracting to my eye ... as I suspect it would be to any top
TPG.
The coin exhibits typical strike weakness consistent with most issues of the Missouri ... best observed in your example by the lack of detail at the high point of the obverse ... Daniel Boone hair above and to the right of his hair is flat and not thoroughly struck.
With this coin in hand you can see for yourself what I mentioned earlier about the special design of the Missouri ... the wide rims and deep recessed fields combine to give the coin a 'medal' appearance ... designer Robert Aitken did a great job IMHO to differentiate this coin from all the others.
I see rim hits on the reverse at 10:00 to 11:00 ... but clean fields ... a few minor bag hits ... worst I can see is on the reverse between Boone powder horn and rifle ...
My opinion FWIW ... the unusual toning and minor rim hits will hold this lovely coin to MS63 ...
Outstanding coin PG!

I know the challenge of pursuing this set in MS ... very well done on this one.
For your grading comparison ... here again is a photo of my PCGS MS64/CAC Missouri .. take an honest look at obverse strike ... my example also shows some strike weakness in the hair ... but can you see the differences?

David