It was intended to replace 1991's Capitol Collectors Series compilation, although track-wise they are identical except for one song. Both albums have 15 tracks, but Classic Masters includes "Take Me" whereas Collectors Series has "Inside Looking Out". The only other difference is the order of the tracks on the disc.
Classic Masters is 24-bit remastered whereas Collectors Series is credited as being mastered from the original stereo mixes. Classic Masters should be considered the better of the two CDs sound wise, but the Collectors Series does have better liner notes.
This CD as a sampler to the recently reissued/remastered Grand Funk catalogue on Capitol.