Wow indeed PG ... Outstanding coin!

Much better in your photos than the prior scans ... there is some weakness in the obverse strike (note the planchet marks on Neptune) ... I have never personally seen a fully well struck Hudson and your coin exhibits the typical weakness on Neptune and the rigging of the good ship
Half Moon on the reverse.
That said ... I am going with MS64 on this one ... perhaps even MS65 .... indeed worthy of a
TPG grade and a wonderful addition to your set.

I truly enjoy Chester Beach design for the Hudson half dollar ... IMHO the funkiest design ever executed as a USA coin ...
C'mon ... the obverse shows Neptune riding a whale (backwards indeed) while a mermaid blows on a conch shell ... and the reverse contains one of the best USA coin fun facts ... Mr. Beach chose to memorialize the good ship
Half Moon with his funky quarter moon hanging in the sky above the ships bow.
I've often pondered as well the stern sail on the
Half Moon as struck on the reverse ... appears to me to be a whale tail ... and just wondering if Chester Beach was having some fun with all of us ... notice how the obverse whale has no tail ... but when you flip the coin over the 'tail' is somehow (with some imagination) incorporated into the stern of the ship.
I suspect Chester Beach is still laughing at getting away with such an amazing and funky design.
Could go on with the history of Henry Hudson ... castaway with his sons on his second trip to the region and never heard from again ...
But the focus here is your lovely coin ... a great addition indeed to your growing set and one of my absolute favorite USA coin designs.
Hoping you find the final two and share some photos of them as well.
Thanks for sharing the photos.
David
Take a look at my other hobby ...
http://www.jk-dk.art