[WalterBright]

My dad dug out of his B-17 navigator's desk a chunk of German flak that missed his head by about an inch. The only reason it missed him was because he had just turned to grab his flak jacket. It was his good luck charm for the rest of his life, and is a prized heirloom. It's about an inch and a half long, just right to carry in his pocket for his subsequent combat missions.

Maybe an heirloom is an object that is simultaneously priceless and worthless.

[nwiswell]

That's a pretty cool artifact, but I don't think it has to be simultaneously worthless -- there are plenty of heirlooms that would be worth money at a pawn shop.

I'd say an heirloom is any object that has a much greater value among a small group of people who are related to each other.

[HideousKojima]

I've got a slide rule that belonged to my great grandfather, who was an architect. Been thinking of actually learning how to use one, I'll probably order a new one to keep the heirloom one in good condition.

[opyate]

My grandad had a tape measure which he regularly oiled and took very good care off.

On the flip side of that, today's tradesmen usually just leave their tape measures out in the rain and mud. Seen it twice now just in my own garden (garden office built in January, and home extensions now in July). Disposable culture!

[flipbrad]

Tape measures become inaccurate over time, especially if you let them snap shut, so holding onto them for too long may not be a great idea.

[coldtea]

If you're building a spaceship maybe.

For anything else it's trivial to check if there's any discrepancy, and for casual use it might not even matter.

[mikewarot]

I have a giant teaching slide-ruler I got from my father in-law's estate. It's missing the slider, and needs a good cleaning. Oddly enough, if you look closely, 2 *3 <> 6, the scale is slightly off. ;-)

Slide rulers are pretty easy to use, and make.

This Illustrated Self-Guided Course On How To Use The Slide Rule [1] seems reasonable.

[1] https://sliderulemuseum.com/SR_Course.htm

[lacrimacida]

This should be your hierloom as well, if your dad didn’t turn his head you wouldn’t exist today.

[WalterBright]

Yup, that thought has definitely occurred to me! When he passed away, we panicked because we couldn't find it. Fortunately, it eventually turned up. He had hidden it for safekeeping.