90% Silver 1970 D Silver Half Dollar?

40% nothing special here.

There were no 90% silver planchets on-hand in 1970. 40% silver halves often show no copper on the rims.

to the CCF!

Yes there was a 1970-D Silver (40%) Kennedy half issued.
https://www.pcgs.com/coinfacts/coin...0-d-50c/6713
https://www.ngccoin.com/coin-explor...s/?des=ms-pl

and from Coinweek a full article on the silver clad Kennedy half in the mint set.
https://coinweek.com/1970-d-kennedy...story-value/
I also see lots of them being sold in Uncirculated sets. (Still in the cello package.)

Sometimes, yes, because it is a silver clad coin.

The cladding is 80% Silver 20% Copper, while the core is 79% Copper 21% Silver.

The core having more copper will be darker than the cladding, but not as easy to see as 100% copper on Cu-Ni clad. Just because you cannot see it does not mean it is not there.

As others have stated, your coin is 99.9999% likely to be a typical 40% silver 1970-D Kennedy half dollar. My advice is to not cut it out of the Mint packaging. A brilliant uncirculated 1970-D Kennedy half can be more valuable than other 40% silver half dollars. As mentioned in the article that Dearborn linked, it was the last circulation 40% silver Kennedy released by the Mint, and the way they did it was unusual. Therefore, the intact packaging might add to the value.

Many times the 80/20 silver-copper clad layers are indistinguishable from the 21/79 silver-copper core. If a 40% coin undergoes significant toning, you might be able to see the core edge as a faint color difference. It might also be more visible under certain wavelengths of light that are reflected differently by copper vs. silver, or with different physical camera filters.

to the CCF and 40%.