[RobGR]

I don't think that piece of plastic would last as long as you think. I think even ABS or PETG would be crumbling to powder in 100 years.

But you could use it as a stamp for thin sheet metal, that might last a longer time.

[stevejb]

Yeah it seems like a cheap CNC drill which can drill holes in steel sheets would be something that would last basically forever. Something like this:

TTC3018 CNC Router Machine 3-Axis Engraving Machine Metal Engraver GRBL Control with Built-in WiFi, 775 Spindle Motor, Engraver Desktop CNC for Wood, Acrylic, Plastic, Aluminum, PCB Milling & Carving https://www.amazon.com/TTC3018-Machine-Engraving-Engraver-Al...

[stevejb]

Hey I just did a bit of a deep dive into this. Wow, thanks for pointing this out. It seems like 'PEEK' would last the longest, but most printers can't do this.

"Standard estimates for indoor PETG longevity are 10–20+ years under normal conditions, with some sources giving a more conservative 5–10 years. A century is 5–10x beyond those estimates under passive conditions." Wow! Thanks for pointing this out. This is fascinating.

[RobGR]

Or, press it into soft clay and then fire the clay.