I'm in my late 30's and have had a 501 since roughly 12. The 500 series are legendary traditional lock blade knives. Normally, you get a nice leather sheath with the 501. Not that it needs is as it is very pocketable, but you do have it for a changeup carry, if you want.
In my opinion, the blade could be slighly longer than it is, considering the handle size. That said, the 501 and 503 will always have a special place in my heart.