John Mayer’s 1961 Fender Stratocaster Hardtail
John acquired this guitar sometime in 2007, which is a presumption mostly based on the photos which seem to date back no further than mid-2007 and the 38th Annual New Orleans Jazz Festival.
According to a Periscope live stream that John did recently [John Mayer on Periscope – Gear Talk] the guitar is a 1961 hard-tail Stratocaster, meaning that it doesn’t have a regular tremolo bridge, making the guitar lighter and less prone to going out of tune.
In the same Periscope session linked above, John mentioned that he used this guitar on ‘Something Like Olivia’, as well as on some other stuff. Unfortunately, he does not go into details about what that other stuff may be.