The sketches are in very good condition- the stamps are in good condition- the mounts that the stamps are in were taped with what looks like 1969 cellophane tape that has gotten sticky all over EVERYTHING near it (thankfully, that was mostly the paper separating the drawings).  It really needs to be removed and the stamps need to be remounted.  Likewise, the sketches should be put into new mats, as the old ones have gotten dirty and a bit ragged....and possibly sticky from the tape.  All 4 of the sketches are in one portfolio.