Producer: Bobby Troup
Cover Photos: Gene Lester
Gatefold cover with pinup photo inside
Outer cover depicts Julie in 12 different monthly themed poses
Liberty burgundy labels with silver print, logo at top of label
Inside cover and record labels state "Liberty Deluxe Series"
Spectra-Sonic Sound
According to Wikipedia, The first gatefold LP packaging used with a traditional 33⅓ LP may have been the Verve release Ella Fitzgerald Sings the Cole Porter Songbook, issued in late 1956, featuring 32 songs on two long-playing monophonic records, on Verve MGV-4001-2.
As said there, that one was a double album which rather suggests a gatefold cover, but it was actually released some months earlier, around June 1956 (sold at costly $9.90, with heavy national promotion according to the Billboard review).
I don't know the original price of this one here, but the Billboard reviewer was very impressed by the cover ("One of the most expensive pop album packaging jobs in some time, this is a double-fold deal with outside covers carrying a dozen pin-up poses of the thrush ...") and it was selected for the (possibly newly created) category Album Covers of the Week ("One of the flashiest covers brought out by the label, this features thrush Julie London in a dozen pin-up poses, one for every month of the year. ...", see uploaded snippet).
This was apparently one of the first gatefold covers ever, and for obvious reasons. As Dr Doom commented on Facebook: Julie London's classic 'Calendar Girl' proving that record companies have been joyfully exploiting women's sexual allure for over 60 years. Does anyone smell cheesecake?
Although the album was only the second entry in Liberty's new "Deluxe Series", it seems that it was the real reason for the whole series. Because of the gatefold attribute, the second half of the year is on the original front cover (actually the right side of the unfolded image), whereas the UK reissue of 1983, which was possibly no gatefold, has the first six months on the front cover.