How do I find out whether a ring was casted or forged?

[digiartist]

There are advantages and disadvantages of casted and forged rings which are not the topic here. I prefer forged rings, but whenever I see a ring, I ask myself how to find out whether it was casted or forged. Is there a simple way to check this? Asking the sales man is an option, but you cannot always trust them. Thanks in advance.