Well, they owe me nothing. I think I paid maybe 20 cents each.

Still, for laughs, I'd like to try to resurrect one.

Some sort of lubricant? Oily stuff would keep the flint from sparking if it ever came loose (WD-40, Liquid Wrench).

Maybe -- irony of ironies -- lighter fluid?

EDIT:
Just checked several others of that batch -- all were seized. But a few sharp cracks on a table loosened up two. And the third, after serious whacking on the bottom and sides, came back to life. I've put a big X on the bottom of all with a Sharpie. Time to use 'em up for the woodstove and firepit.

Pardon the uber-nerd commentary. "How to field strip a Bic lighter?" Oy. But it's still a more practical hobby than stamp collecting.