The Medallion

Season 3's "Relic" explored a time period when Jor-El visited Earth-- specifically, Smallville, KS.  Jor-El called himself "Joe" and was remembered by the townsfolk as wearing "a distinctive medallion."  Below is an artist's sketch of Jor-El that was published in the Ledger (note the necklace).  Next to it is a matching glyph on one of the cave's walls.

In "Relic," it's explained that the symbol on the medallion means "journey," but exactly how this translation fits is unclear.  The Kryptonian Symbols and Writing page explains a concepts is sometimes represented with a composite symbol that incorporates its individual letters (like "hope"), but "journey" doesn't seem to be an example of this.  If one treats the necklace's shape as part of the symbol, then this border plus the figure-eight make up the letter S.  If one does not consider the border to be part of the symbol, then the figure-eight alone is a letter G.  If there were two dots above the set of two lines in the center instead of just one, that could be an upside-down A, a U, or a Y depending on where the other dot would be placed.  The little rectangle with a line coming out of it at the bottom looks like part of the letter E.  Another possibility altogether is that the figure-eight and rectangle are a stylized version of the letter K, but that still wouldn't explain the middle part.  At any rate, it's obvious that no amount of symbol-fiddling can turn the above into "journey," so it's probably just meant to be a cool-looking symbol that screams "S-shield."  When Jor-El finished his trip to Smallville, he put the medallion in a recession hidden behind the symbol, which Clark later discovered.  See the page on Jor-El for more info.