There is no real point to have it slabbed right away. Even if they would encapsulate it, it will only get a details grade. I too asked the same question when I found my cut Pine Tree and my Oak Tree Shilling. Many colonial coin collectors would rather be able to feel the coin in their hands than to hold a piece of hard plastic. When it comes to value, its minimum several hundred dollars. $1,000-$2,000 isn't out of the question if the right people are around. There are not a lot of pieces of cut Massachusetts silver that I have seen or heard of. Bill Ladd, Bill D., Silver Tree Chaser, myself and maybe one other person on T-net have posted found examples. There were several found in the wreck of the Feversham, see the link below for some really interesting info on cut Mass Silver.
Mid-island coin club: A Malay Communist IssueHere is a cut Pine Tree Shilling that sold in 2008:
Stack's : 1652 Massachusetts cut Pine Tree shilling. Originally Noe-5 or 6. AG-3 (AN06949230)