Columbia Masterworks label released records from 1927 to 1980. After that, it was separated from the Columbia label and renamed CBS Masterworks.

Please note that starting around 1958 possibly into the early 1970s, LPs on this label list two catalog numbers on the sleeve: an ML number (for the mono recording) and an MS number (for the stereo recording). Check the physical record to determine the version of your copy.

Columbia Masterworks was renamed CBS Masterworks Records in 1980 and removed from the Columbia label.
In 1990 it was again renamed Sony Classical Records because of the sale of CBS Records to the Sony Corporation.

The Masterworks brand is currently used on Masterworks Broadway Records as well as Sony Masterworks, Sony being the parent label for both.

78 RPM album sets may have multiple catalog numbers on various parts of the release. As always, please try to enter all of the variations, along with release notes explaining what number appears where. Records with "AM" or "MM" numbering were configured for different types of record changers. AM has the sides in sequence across the front of each record (e.g. A = side 1, C = side 2, E = side 3), then continuing with the back of each record from the first to the last (e.g. B = side #4, D = side #5, F = side #6). MM has the continuation from the last to the first (e.g. F = side 4, D = side 5, B = side 6).

Overview of US catalogue prefixes:
ML 1948 - 1967 Regular Columbia Masterworks mono releases (ML 4000 - ML 6999)
used for Classical and closely related releases.
MS 1958 - 1970 Regular Columbia Masterworks stereo releases (MS 6000 - ML 7999)
used for Classical and closely related releases. For the MS series, the last two digits of the number match those of the corresponding mono release, but there is a difference of 600 between those two. So MS 6476 is the stereo release for ML 5876.
KL 1955 - 1968 Regular Columbia Masterworks mono releases (KL 4000 - KL 6999)
used for Original Cast, Original Soundtrack and few Classical releases.
KOL 1959 - 1968 Premium Columbia Masterworks mono releases (KOL 5000 - KOL 8000)
this was probably a premium series.
KOS 1958 - 1968 Regular Columbia Masterworks stereo releases (KOS 5000 - KOS 8000)
this was probably a premium series.
KS 1958 - 1968 Regular Columbia Masterworks stereo releases (KS 4000 - KS 6999)
used for Original Cast, Original Soundtrack and few Classical releases.
OL 1955 - 1968 Regular Columbia Masterworks mono releases
used for Original Cast and Original Soundtrack releases.
OS 1958 - 1968 Regular Columbia Masterworks stereo releases
used for Original Cast and Original Soundtrack releases. For the OS series, the last two digits of the number match those of the corresponding mono release, but there is a difference of -3600 between those two. So OS 3180 is the stereo release for OL 6780.
BOS 1967 - 1969 Premium Columbia Masterworks stereo releases
those releases had a higher list price than regular albums in the OS-Series.
M 1970 - 1980 Regular Columbia Masterworks M-30000 series
used for Classical and closely related releases.
MG 1970 - 1980 Regular Columbia Masterworks MG-30000 2LP-Sets
the letter G stands for a double album. Alternatively the prefix M2 was used for a 2LP-Set, and M3, M4 etc. for box sets with more albums.
MQ 1972 - 1974 Columbia Masterworks Quadraphonic MQ-30000 series
S 1970 - 1980 Regular Columbia Masterworks S-30000 series
used for Original Cast and Original Soundtrack releases.