need help with old receivers tone controls

I have a vintage Marantz 2265 receiver that is used in my study for very low level-nearfield listening. It has a loudness compensation control which I find very useful for extremely low level listening. It also has bass, mid and treble tone controls...and it has a control called tone mode. The indents are labeled out and in which I obviously understand, and the other indents are labeled 100Hz 10kHz 100Hz/10kZ. Are these low, high and combined low high cutoffs of frequency response? There is no manual to refer to and I'd like to know exactly what these cutoffs do and why they were designed into the unit, unless they were a market driven item during the "age of the equalizers".
Those are probably 'hinge' points where the roll-offs begin.

For an exact answer, you can purchase a manual at the following ...

Marantz 2265 manual .

Regards, Rich
The knob does select the turnover frequencies for the tone controls. With the knob 'out', the tone controls are bypassed regardless of their settings. With it 'in' the turnovers default to the broader band responses of the day, bass frequencies below about 400Hz are affected by the bass control, treble frequencies above about 3KHz are affected by the treble knob. The tone mode knob allows you the option of adjusting just the frequency extremes for bass and/or treble at the turnover points listed. Current amps with tone controls usually default to these more-extreme points so as to have no effect on the midrange, despite there being little musical information below 100Hz or above 10KHz. You should be able to hear the difference at louder volumes and full-range spkrs by putzing with the tone controls/turnover frequencies.