Preserving and displaying brass tokens

Please pardon the intrusion, as I am not a coin collector, but I'm
hoping someone here has a quick answer...

I want to display and preserve two brass tokens in a frame (one
showing the obverse, one showing the reverse). These tokens have no
value to anyone but me. They will be fresh from the mint.

I have found very little on the net about preserving new brass tokens
or coins, so I am at a loss as to what I need to do to prevent them
from tarnishing. Do I need to encase them in capsules before framing,
or do I just need to make sure they are mounted in an acid-free mat?
Do I need to do anything to the tokens to prepare them before
mounting?

Thank you for any insight you can provide.

--Chris