I think that
good advice has already been given. No expert
conservator here either, but the only safe way to "seal" a coin
per say that I know of is to wax it.
Now, as far as using
Ren Wax, I would personally recommed Conservator's Wax in this instance. It is the same stuff, but I use it instead. From my understanding it is a little more jelly like to begin with so may be easier to apply in this case. You could always warm the wax slightly as well to soften it up to apply it easy. It will turn almost mayonase like.
Also, if you are aftraid to heat this coin up due to small thermal expansion that may occur and possilbly
crack or
pop pieces off of the coin, then put a very thin layer of wax on it and then melt the wax onto the coin with a blow dryer. This, IMO, will keep the coin cooler, but melt the wax to the same effect.
I have only done a few coins with Con Wax, but I never really found buffing necessary. I think they look
good without the buff. Just my opinion.