My dad just acquired an old martini with excellent metal. However, the stock looks like it was wet, so is weather checked and shrunken with some small open cracks in the grain. Any suggestions on how to restore the original wood?

I've done a couple of stocks like you're describing. I strip 'em down to the bare wood, use a good filler, then sand and finish. The filler is from Brownell's.

http://www.brownells.com/aspx/NS/store/ProductDetail.as...title=STOCK%20FILLER