In a recent issue of Uncanny Avengers, a flashback to the 11th century AD shows a young Thor still using the axe Jarnbjorn, which he wielded prior to becoming worthy enough to lift Mjolnir. But earlier stories showed him already having Mjolnir before the time period in this issue, as far back as the mid 10th century and probably before then. So how come he's still got Jarnbjorn here? It doesn't make sense.
