I have been asked this question sooo many times

Technically, it's 3D, but it's just an imitation of 3D model :D

I made it by creating two sprite objects and merging them with a C# script.

In detail: the script generates a mesh in runtime between two sprites.Once it defines geometry it starts mapping UV for side material and keeps repeating this process until it reaches the opposite edge

Q: Is this better to create a 3d model of coin?

A: Nah :D This way is much funnier!

So go play the game and see it for yourself!

Submission - https://ldjam.com/events/ludum-dare/58/seven-day-bargain