The average superhet was constructed with seven or eight vacuum tubes. Because of that, some had cabinets that were exceptionally long compared to other circuits of the day. Cabinets up to forty inches were not uncommon. However, there were some condensed to a panel width of only a foot and a half.
     Beware, just because a set has seven, eight, or nine tubes in a huge cabinet, does NOT mean it's a superhet. In the late 20s, to impress potential customers, TRFs were over-designed to use many tubes. After RCA's patents expired, tubes were "cheap" and it was the fad to throw a bunch into an ordinary radio with no regard for extra noise and distortion.
     Always look for a line of enclosed IF/Filter transformers and closely associated tubes as an indicator it's likely a superhet. Also, look for a variometer used as the variable oscillator coil. Some supers used a standard coil with a small variable capacitor strapped across it for the oscillator circuit. Finding these specific components inside the cabinet will help you identify whether or not it is a superheterodyne and not an exploited TRF.

     After 1927, most fly-by-night kit manufacturers faded from popularity. RCA would only sue those companies that could make huge fortunes from building and selling superhets. So, that opened the door for small companies to manufacture and sell nearly finished supers. That's when companies like Scott, Remler, Silver-Marshall, and Lincoln began displaying their names openly on front panels. Again, caution, not every Silver-Marshall set was a superhet even if it sported seven tubes.