There is supposed to be some sort of rub 'n sniff trick to tell the difference. Check the help files.

As far as preserving celluloid, I think the main thing is to keep them out of direct sunlight, and if you have celluloid-scaled razors, check on them every once in a while, and consider storing them separately from other razors. When they do decompose the effect on steel is devastating as well as "contagious." Go on ebay and look at the photos for any large "straight razor lot" – when fifty razors or so are laid out together you'll see sections within the lot decomposing together like so many lepers.