The Tektronix 067-0543-99 is an instrument for measuring DC voltages from from a few millivolts to 11 kilovolts. It uses a precision voltage divider and an Airpax A175 chopper to compare the input voltage with a reference.
Regarding this instrument, Stan Griffiths says:
There are actually TWO versions of this thing. One is much more common than the other and that is the one called the 067-0543-00. The other one has the same measurement capability but is only half as wide . . . the size of a 284 . . . and has no Part Number. It is just called "DC Voltage Bridge". Both styles have serial numbers and the 6 digit type with no letters. The 067-0543-99 is the size of a 184, 106, or 191 and will fit into the same type of cabinet as those instruments will.
On the front panel of the normal 067-0543-00 are a pair of light bulbs that are driven by a comparator circuit. Both of these lights are [illuminated] when comparison occurs. When a voltage to be measured is connected to the input binding posts and the polarity switch is in the correct position, the range switches, consisting of the rotary switch on the front panel and the 10 position switch surrounding the Duo Dial, are set to the correct range, the Duo Dial is rotated until the lights extingish. The measured voltage is then read to four digits from the range switches and Duo Dial. The signal driving the comparator lights is also fed to a BNC connector on the front panel called "Difference Output". You can monitor this signal with your bench scope and find the null by looking for minimum signal at that BNC connector. The small version of the DC Voltage Bridge does not have the comparator light circuitry or lights in it but it still has the BNC connector so in this case, an external scope must be used as an indicator. You might be able to use a sensitive AC voltmeter as an indicator but I have never tried it. I think the "Ripple Output" BNC is a convenient place to AC couple to the power supply under test so you can measure power supply voltage and ripple at the same time.