This was made between 1909 and 1920. Ebony holds up well.
This was made between 1936 and 1952. Bone holds up well.
Buy what you like the best. I'd buy a double blade though. I actually use my main blade for almost all my cutting needs. I use my pen for everything else; scraping, poking, digging, etc. Basically, I should just have a knife with a punch secondary. Haha.
I have a new mid-tech knife coming soon! The Dart Personal Knife will be out around March 2015. Email or message me for more details. The website will be up soon.