How can you tell if a crystal is glued or pressed in?

[hackR]

as the topic says, how can you tell?...assuming you are planning to use a crystal press to remove/reinstall it, does it matter?...does a glued in crystal need to be reinstalled via glue or can it be pressed in?...

re: glued in crystals...is there a best solvent to use to clean it up prior to reinstallation?...if glue is needed to put it back, what kind?...

full disclosure...i am curious about all this...i may have a watchsmith remove some crystals...i have no clue if they are glued or pressed in...so wondering if there's a way to tell...and what issues/problems might arise with working with a glued crystal...i doubt i'll ever do this myself -- but you never know...so i'm just trying to learn...if there's a post on this, i cannot find one...

thanks...R