Ahhh, the graphic equalizer !
A staple from Victor since 1966, graphic eqs are far less useful than a good old parametric but oh so... graphic :)
The SEA-R7 wasn't the biggest from the lineup but the one that held much of what is now the present in any receiver and home-theater system (in other words 90% of the market) : delay simulation.
Nothing new then and certainly nothing new now, but the SEA-R7 had a dual-channel twist : for each stereo channel, the delay is applicable separately to five specific frequencies with an overall delay control.
So instead of diluting the entire signal into reverb and late reflections, one can add a tad of depth at any (or all) of the five frequencies available. Said frequencies are all under 500Hz so as to avoid the aforementioned dilution.
A nice trick is the use of dual-color LEDs to indicate the delay depth chosen : green for none, red for out there in the sticks and orange for a pleasantly enlarged living room.
Besides this high-end feature, and an early alphanumerical display, the rest of the SEA-R7 is like any other graphic equalizer but for the circuit and componentry which was, as often with Victor, carefully chosen to avoid having (too much) problems with phase rotations, noise and distortion.