That could be just about anything, but I would assume it is nothing super important because those are connected by wires and stuff. Of course there is no way to really tell without opening it up, but I wouldn't worry. If you really want to know what it is, you could open it, but you risk causing damage while doing so.

I will email my city's public works & engineering today. But what should I email them about?

The computer is the cause, as it don't shimmering when the computer is off. The voltage on that phase, is usually 200-210V.

I cannot see it in the video.

Is it behind a dimmer? Dimmers are very sensitive to other devices on the grid causing interference.

Your computer may be causing that interference. In earlier days people would quickly complain about that because it makes AM reception impossible, but today it can remain undetected until things started acting weird. This is also the reason why fluorescent fixtures are required to have suppression capacitors (at least in europe).

If it is not just your computer causing this but the issue also shows up when you connect a 300-500w incandescent lamp or a heater on the outlet where you normally plug in your computer, and your lamp starts flickering randomly, this means there is DANGER. With the small load of the lamp there is no problem, but once extra load is turned on, a wire nut or other mains voltage connection starts to heat up and spark, causing flickering. This is very dangerous.

I agree with RRK, the lamp design itself dates back to the 40s. In y opinion it is most likely o soviet copy of the german Osram Na Spectral lamp, that was adapted. Then this amp was continued to be manufactured by chinese manufacturers as a cheaper alternative to the rather expensive Osram lamp.

I also agree that in dedicated laboratory lamps the developmental steps are not too big. Reason being is the small market were there is also the redness to pay a bit more for a lamp. The possible profit margin for new investment is rather small.

Facebook Marketplace, Craigslist.

Out and about– email township or utility officials. Our local lineman won't answer an email, but if you catch him in his bucket truck on the job, you can take whatever he's removing home.

Thanks Drew. Any idea as to what causes the rattle in the first place? (I get "impact", but what actually broke loose?)

You can verify if the rattle is indeed caused by the casing by holding it in place while shaking it.

If it is the casing, some hot/super glue would probably be enough to eliminate the rattle if it bothers you.

I dropped my Sigma Instruments / Fisher Pierce 7701 Photocell about 1ft, onto a desk top while cleaning. It now rattles.

Anything I can do to fix the rattle? The casing moves around now, which I assume is causing the vibration...? Thanks.

My guess is the area of optical measurements is rather conservative so once the instrument was established around 1930's with first kinds of LPS lamps, it continued to be ordered by labs over 40 years span.

Also may be this early design had some advantages over later LPS lamps in radiation quality like spectral purity, but here I am not sure.