No, it's never been discussed on here before. I don't think it has ever been stated why he had it. At least not in anything that I've ever read, but I am not a die hard researcher either though, so maybe someone else will know. But, I am just guessing it is probably something he just liked and thought looked cool.
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“And may you grow to be proud
Dignified and true
And do unto others
As you'd have done to you”