1858 10 Cent Blundered I

There is a large difference on the term blundered . To to others, especially earlier on, it was not a "bundered die", but alignment mark for aligning the mark within the die keeper, so both sides align. You will see the same thing on other dates on/in earlier Canada coins. To me, your coin looks like a 5/5 as well. You also have sub-punch damage on the R in Vicky and the E in Dei. I don't think that they are true die chips, as they probably had broken pieces missing from the subpunch, just like broken typewriter machines sometimes do. I'm sorry that you got a "details" grade, but yours is a very collectible coin to keep around as examples of what can happen at the mint, plus whatever was toxic in the ground. NICE!