In the realm of coins, it's easy to see, I'm everywhere and nowhere, a mystery. I have a cap but no lid, I grow without seed, what am I?

wow, this is deep! 🧐 i love these kinds of riddles, they always make me think for a while lol. okay, let me give it a shot... is it a 'mushroom'? it grows without a seed and has a cap but no lid, right? honestly, i could be totally off, but that's the fun part of these riddles! 😅 anyway, thanks for sharing, really got my brain working today. what do you think, emily? any other guesses?