I'm going to say that if you can work around the nail holes it will probably be alright, but i've never tried it myself. I think it is definitely worth a try given it's history.
It is a reaction between the iron in the nails and the tannin in the wood, and it gets darker the longer the exposure is. The process of this reaction is called "ebonizing", you can exploit this reaction to stain any wood with a high tannin content using a solution with a lot of iron in it, typically it's done by soaking steel wool or other sort of non-stainless steel in vinegar and painting it onto the wood. This is the same reaction just over a long time of iron leeching into the wood. As far as I know I've never heard of it affecting the integrity of the wood.