Actually Marantz made a number of products(tuners and receivers) with a built-in scope. The scope provided vast info for FM stereo reception including signal strength, multipath and center channel tuning, all simultaneously. 1 standout product was their 2600 stereo receiver, had a 3" scope, 5 gang quartz-locked FM analog tuner, patented servo-controlled tunnel output stage, rated @ 400Wx2 into 4 Ohms @0.05%, 20Hz-20kHz. Its power output was actually certified by the Federal Trade Commission, as back then there were alot of BS claims about watts. Originally sold for $1695 in 77/78, now they sell for up to $25K if in good working and ID condition. The 2600s' amplifier circuit and tunnel was used in the Marantz 510 pro-audio amplifers, used by many of the top-rock groups including the Eagles, Rhonstadt, Jackson Browne, CYN for their touring concert systems. Note the Eagle's system used 75 of the 510 amplifiers. The challenge of the AR3As was their low sensitivity and 4 Ohm impedance plus being a sealed enclosure, also the dome tweeter was on the bright side but back in the 70s' considered 1 of the top loudspeakers..
Just my $0.02...