23EGP22 data sheet can be found at
https://frank.pocnet.net/sheets/202/2/23EGP22.pdf
Outer diagonal is shown as 23 11/32, +3/23, -1/8;
Useful screen diagonal 22 3/8; useful width 19 7/32, useful height 15 3/8.
19.21875/15.375 = 1.25
Notice that this is narrower than the standard image aspect ratio of 1.3333...
This meant that the active trace time could be reduced from about 63.6-10.9 =52.7 microseconds to 49.4 microseconds, increasing the retrace time to 63.6 - 49.4 = 14.2 microseconds, which would crop the sides without geometric distortion of the image.
This increase in retrace time by 30% was very advantageous for reducing the peak voltage on the horizontal output transistor in solid state sets.