I concur, it does look like a silo lid, but the scale suggests it’s rather smaller than that, around 1m diameter?

After reading the thread, I'm going to risk a well cover.

There was a mysterious underground bunker or silo or something within which someone needed to enter a code every so often. It was a pretty big plot point and served to bring a lot of tension to the series, because what would happen if you didn't enter the numbers on schedule?

Heres a random forum with a picture:

https://www.tigerdroppings.com/rant/o-t-lounge/how-many-of-you-45-year-old-baws-remember-old-school-tv-antennas/117396033/

Second post with picture, trying to link it directly somehow goes to a reddit post.

But yes, eventually tech was good enough they could do it with mesh. Before that they were solid metal.

Like I said, this look like an old one.

But you should really try asking questions instead of just confidentally being wrong and waiting to be corrected. I tend to block people like that pretty quickly, and so do other people who take the time to explain things.

I wonder if there are satellite dishes like this that come flat packed and you need to assemble it.

Pretty much only explanation. The strips aren't as good as solid, but if the tech that allowed mesh existed they wouldn't have to try to maximize surface area still and could use mesh panels.

It's one of those weird products that as soon as it solved a problem (shipping a complete fish to remote area) the real problem (needs a solid dish) got solved.

So they probably weren't popular for long, but also might not have had a reason to replace the physical dish for decades.

Even when people stopped using dishes in general, they tended to just sit there. Which also makes "dumped off a cliff" a likely explanation.