This is CW article outlines what cladking is frequently posting re sets and moderns...
Full article:
http://www.coinworld.com/news/022706/BW_0227.aspProof, Mint set survival
Coin demand forces disassembling
posted 2/14/06
By Paul Gilkes
Coin World Staff
The surviving number of Proof sets and Uncirculated Mint sets issued by the United States Mint may be smaller than many may think.
Each year, the Mint produces sets in quantities ranging from hundreds of thousands to the low millions, for dealer and collector consumption.
Not all of these sets, however, remain as sets in their original packaging.
Untold thousands of sets are opened annually, driven by collector demand for individual coins within those sets.
Click on image to enlarge
COLLECTORS WANTING a 1970-D
Kennedy half dollar to add to their collections have to purchase the Uncirculated Mint set for that year or buy a coin removed from a set, since no half dollars were struck for circulation.
That demand for individual coins can drive up the price of an intact set and encourage the breaking up of sets, with the individual coins sold to the collecting populace.
Just how many sets are broken apart is uncertain...