Sonomatics were aways round-wound. The 340 Sonomatic Medium set was was .012-.056 up until sometimes during the 1970s. They originally had a .028 wound G, and then someone at Gibson woke up and lowered it to a wound .024. The most famous user being Pete Townshend, who tossed the wound G for a plain .016, and around 1972, changed to a .018. The Sonomatics sets were also available in .012-.057, .011-.056, and the 340L: .011-.052. In the early '80s, when the packaging was changed to blue on grey. the G string was raised to .025, and the D string was raised from a .032 to a .034. In the '90s the set number was changed to 900M, and eventually to L5 Mediums. For most of its existence, the Sonomatics were a pure nickel string. The Mona- Steel 240 set was was a Monel string .014-.056.
Gibson's flat-wound strings were called "Hi-Fi " stainless steel. The Medium 040 set was gauged .014-.058; the 040L Light gauge set was .011-.051. In the 1990s, they were relabeled "Flat Wires."
For many years, Gibsons guitars and basses came with a hang tag stating what strings were the guitars left the factory with.
Hope this clears up myths and misinformation.
