The 1973 Solid Bodies brochure is a single sheet with a folded flap - the image below shows the contents within the fold: specifications and finish options for the Gibson SG Custom, Gibson SG Standard, Gibson SG Special, SGI and SGII guitars. One notable omission from this brochure is the SGIII, which is actually identical to the SGII, but with a cherry sunburst (rather than cherry or walnut) finish.
The Standard is available for the first time in Natural Mahogany finish (aswell as Cherry and Walnut) - actually the previous solid body brochure (1972) listed the SG Deluxe and SG Pro (which could be argued were the Standard and Special under different names) as available in Natural Mahogany - though note the SG Special is only offered here in Cherry and Walnut.
All five models described here have identical body dimensions, 22 frets and rosewood (or ebony for the Custom) fretboards. And all were available in translucent Walnut and Cherry (again, except the Custom) finish. Besides the obvious hardware changes between the models, the biggest difference was the mahogany body and neck of the top three guitars versus the unspecified 'hardwood' neck and body of the lower two. SG I and II bodies would typically be alder, with (typically two piece) laminate maple necks.
$135
$3250
$3250
$2200
$2000
$5939
$3190
$3999
$2200
$2195