There is a lot of stuff in your gadgets, possibly more than you know and in a lot of reports over the years, apparently Apple has been shipping MacBooks with different coins located within. No one knows why but if you own an apple product, you might have some loose change among your hardware.
I wonder if the coins does a task like being a spacer to keep the disc drive from bending, or warping. Coins like pennies, dimes, and quarters are made from very hard metal.
Some people believe throwing coins in water fountains, rivers, ponds, and oceans and keeping coins in boxes or piggy banks give people good luck, so a superstitious person may put a coin in a drive to give them good luck, or the owner of the drive good luck.
I think coins are mainly in Macbooks with Disc drives like a DVD-ROM drive.
The Macbook stop including disc drives in 2012 because the Macbook Pro 2012 is the last laptop which come with a DVD-ROM drive.
The iPhone, iPad, iPod, and newer thinner Macbooks like the Macbook Air are less likely to contain coins because they are very thin, but it is possible a few of them contain coins left there by the workers who maybe bored, and decided to put a coin in them for fun.