It’s four-sided, not two-sided. If that one counts, you can also just use a regular six-sided one and just put three ‘ones’ and three ‘twos’ on it.

define ‘side’.

How many sides on a ball?

This die can only ever land on two distinct sides so it has two sides.

This gave me an idea for a gimmick die. Transparent die filled with dark liquid. The exterior of the die has the usual numbers in white lettering. Inside the die, there is a smaller cork die that rises like a magic 8ball. It’s 2d(x) in 1. Interesting for tension building, if nothing else.

Edit: looked it up and I’m not original, and they’re largely as bad as I thought they’d be

Incorrect. It can land on two different sides. Or it can roll off the table and under something, leaving you in a state of limbo.

The odds of a US nickel landing on its edge is about 1 in 6000. If there are any other country’s coins thicker the odds would probably get better.

I’m a bit disappointed that many of these n-sided dice are not isohedral, despite isohedral polyhedra existing for many of these values of n.

The weirdly shaped ones probably sell better. Which would you pick up in a store?

I’m really surprised that this does not seem to be an existing thing for d10s specifically. I can find nested d10s and there are heaps of liquid core dice, but apparently none that combine those two ideas

Don’t be ridiculous, obviously you roll a d20, subtract one, and then count how many digits the result has

It’s called a chance cube and it’s essential on tatooine

The old UK £1 was similar in size but twice as thick. It’s now 12-sided but not sure how that impacts the odds.

Oh, I still bought the full set, but I tried to get isohedral dice whenever possible.

It has only 1 corner, and 2 surfaces, making it 2 sided. The 2 sides just happen to be curved

I know there’s a way to figure that out, but I have no idea where to start. So I’m going with 1 in 3000, plus or minus 42.

4 sided.

Roll a d100, if it is odd 1, 2 if even

Fair point. A ball has either one or infinite sides from my perspective.

Inside, outside, and, depending on the ball, offsides.