Does anyone here collect Zippo lighters? I have a few but just picked one up at a rummage sale today and I'm stumped as to how old this one is. It's a slim lighter, and on the bottom there's only the zippo logo with the little "R" registration circle, and that's it. No dots, slashes or anything. I went to the zippo site to try to find the date but no luck. If anyone can help me, it would be most... helpful? Thanks in advance.