i read this post yesterday and realized my dad had one of these things on his keychain while i was growing up, along with a little circular piece of metal with 4 different size flathead screwdrivers on it. anyway, i finally realized what this was and i went and picked one up today. i got home and showed my dad and his eyes lit up... he served our great nation in Vietnam... he said he'd like a few so i'm going to buy and handful tomorrow. i honestly can't think of any reason to not carry one any where you go. however, the only problem, if it can really be considered a problem, is that they only had the larger P-51s, but my dad said that was actually probably better anyway. just something to consider, if you don't have one, make it your next EDC purchase... i did.