Excerpted from: http://www.geocities.com/rf-man/cb/index.html
The Atlantic City Conference - Amateurs lose parts of 10 meters and 20 meters, but will gain a new band at 15 meters in 1952. To compensate for the loss, the FCC allows use of the 11 meter band (26.96 to 27.23 Mc) on a shared basis with Industrial, Scientific and Medical [ISM] devices. Class D radio for shared professional use introduced at 465MHz UHF but was too tricky for the time and didn't catch on. Doctors permitted to continue using 27MHz. [for diathermy]
Firestone Tire Company granted experimental license W10XXD for 27.255MHz using two 3Watt transmitters.
* 465MHz Class D service deemed a failure, the search is on for a replacement band.
* Early 1957
FCC Docket #11994 proposes reallocating Class D in the very underused 11 meters Ham band 26.96-27.23 MHz (USA-only). At this time there was little business/military use of 27MHz and model control on 27.255 was inadequate, being shared with paging and other services.
* 11th Sept 1958
The 11 meters ham band is reassigned to models and Class D Citizens' Band radio. The band is divided into 10kHz channels, the first channel bounded by 26.96 and 26.97 with the carrier frequency centered at 26.965 - and 27.225 being the last channel center - 27 channels in all. Models were allocated 5 new channel centers, 50kHz apart, the outer channels being 35kHz away from the band edges. 22 Class D channels were arranged around the model channels that later became known as channels 3A, 7A, 11A, 15A and 19A. The old model channel at 27.255 was allocated as a further 23rd Class D channel, a shared frequency that remains as the 6th model channel also. The Business Band above 27.23 couldn't yet be used for CB apart from channel 23 - the two-channel gap between 22 and 23 gave rise to pirate channels 22A and 22B...
My thanks (for info) to : The Wayback machine, Richard McCollum & Meg on rec.radio.cb, Retro-Dave (RetroCom 27Mc museum)), WoodyWorld CB pages, 'the author' of 'UK Bands'
25.7 Mc would be a little too low for the shared 11m band, and, as you note, 1959 would be a little too late, at least in USA, 12m ends just below 25 MHz, plus wasn't allocated until about 1980, following ITU WARC-79, however there is an 11m AM broadcast band from 25.6 - 26.1 MHz -- perhaps it's a one way SWL QSL?
As to 465 Mc in the late '40's WHAT were they thinking!? 4m (72-75 Mc) -- now used for radio controlled planes/cars/boats/etc. -- might have been a better choice in that day and age.