1. Are there any modern (in production) equivalents of those "bubble display"s? I have a project where I need tiny 7-segment displays (curernt displays beside each USB port). But those "bubble display"s have become expensive collectible "historic artifacts".

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2. About 20 mA for a single 5mm LED is not particularly high until quite recently. All the way through the 1990s this was the standard current for indicator LEDs. Nowadays with multi-quantum well structures and InGaN LEDs you get the same brightness from just a few mA, but even your MAN72 were specified for 240 mA total continuous forward current with all segments lit – even higher when used in multiplexed displays.

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3. Hi Fran,
   fun fact: this type of display came back some years ago. Look e. g. for Mentor 2274.1005. The idea is that you can use SMD LEDs of your choice while you have the guarantee that the case dimensions, segment style and size stay the same. When I remember correctly Adafruit has quite large display using the same principle even with multicolour LEDs.

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4. The year I was born.

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5. I was an electronic tech in the steel mills back in the 70's. We had controls that used mechanical readouts that were controlled by BCD. They were very unreliable and the operators would have to pound on the control panels to get the readouts to work. We replaced those readouts with these same Dialight readouts in red. They worked great and the operators loved them no more pounding. Power consumption was not an issue as these controls had massive power supplies and the led displays actually used less current than the mechanical ones. This brought back some old memories.

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6. You can make excellent light pipes from hot glue. I was thinking that you should do a video on the very earliest "Price Is Right" displays when the first items went up for bids and they used digits made from 35 (7×5) light bulbs each segment. For what ever reason they changed over to their own green and orange seven segment displays by 1974. They still used the light bulbs in other parts of the show, such as the showcases however. Thanks for being the "Queen of displays"!

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7. Fran, here's a tip for a safe pin header power supply pinout. Use three pins, outer two are ground and the inner one is power. That way you can insert it either way and not let the magic smoke out.

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8. Amazing color. Reminds me of vaseline glass.

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9. I'd guess that "Sigma" logo stands for Signetics?

   Makers of the 555 timer and the 25120 9046-bit Write-Only Memory.

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10. I don’t want to see another eye searingly blue LED on a modern product again, only these!

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11. I don't know why but I've always found green the least interesting LED colour. It's not that I don't like the colour green but with LEDs it's always this pale yellowish green colour that's not very pronounced. My oven and microwave both have a green LED panel and I've even thought about opening them up to change them for red LEDs 😂

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12. Is it weird that I think that this looks beautiful?

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13. "S" logo on the 7447 BCD to 7 segment chip is Signetics, most famously known for the 555. Philips took them over in the 70s.

    I was making stuff with 7447s in 1977 when I was 12, when I designed and built a TTL clock, with about 20 TTL chips. It took about an amp at 5V! It was controlled by the line frequency, so when the washing machine ran it would count up hundreds of seconds when the machine's cycle changed 😉

    You could always tell when a 7447 or 7448 was being used in an application because the top of the 6 and bottom of the 9 were missing.

    Possible application is gas pumps, although the first digital pumps I remember used 7 segment incandescent filament displays.

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14. It looks like they had the 3mm and 5mm standard size then too.

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15. The first large led displays I remember seeing were in the mid 1980s…

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