It will be fine Gene. If you think about it, "sealer" is really a misnomer (unless you are dipping it into polyurethane
) All the sealer does is slow down the rate of change. Unless you are exposing it to extremes in humidity and temps the wood should adapt with no problems.
JohnH: I do apply a coat of finish to the out side of the inner back. What I do is run a strip of masking tape around the edge where the blocks will eventually be and give it a shot of spray lacquer. Also, after gluing the blocks onto the outer back I mask off the tops of the blocks and give what will be the inside of the outer back a coat too.
This is just for sake of appearance.....to give it a uniform color after the rest of the instrument is finished. I found that if I don't do this I can get a shadowing effect on facing surfaces of the backs where the spray finish process doesn't reach.