The actual way eggcrate displays work is that they use diodes on an internal ROM card to map each pixel in the display.
When a signal pin is connected to ground with common referenced at +28V, the current is steered through the diodes and directed to the appropriate bulbs to be lit for the selected symbol associated with that pin.
That, @price_authority, is how these displays work.
There was no ROM in the original Display Systems readouts. ROM is read-only memory. That would require two separate power supplies: variable 0 - 28V for the lamps and 5V for the ROM chip. The lamps had to be dimmable. The ROM chip probably could not deal with a variable voltage. It would also require a way to program the characters into ROM. The old DS readouts were exclusively diodes — no ROM.
Lamp-matrix readouts were used in the '50's and '60's on Twenty One, Tic Tac Dough, The Price Is Right and Say When!! At the time I don't think solid-state diodes had been developed. I think they used a different technology, possibly involving relays. The readouts used on TPIR and Say When!! came from American Totalizator and were also used for race-track betting displays.
When TPIR first came to CBS in 1972 there was an asterisk as the first character in the readouts in contestants' row to indicate the winner. This took the place of the dollar-sign character in the readout. When they went to seven-segment readouts the asterisk was eliminated.
In the movie Quiz Show they did a remarkable job of re-creating the isolation booths on Twenty One. I have a pretty good eye for detail and the readouts and the mics were spot-on. I don't know if Ted Cooper was consulted for the movie, but he worked at NBC NY at the time so he may have been. I understand Ted worked on the "slips" for Concentration, the two boards that displayed the prizes each contestant had accumulated. I was once on the set when Classic Concentration was rehearsing. There was Steve Ryan supervising the slips. He had two stagehands operating the slips and it was WORK. They loaded a prize card every time a contestant called a number. If there was a match, they revealed the prize card; if not, they took down the prize card and awaited the next number to be called. Whew! It was WORK!