Darren,
That die certainly looked like it was lettered on the wrong side. Always feed the heavy chamfer on first.
I have seen these dies before, in fact I think I have a couple somewhere. As far as I know, they are used in a production environment where a setter presets the cut. So all the operator has to do it lock it into his dieholder with no further adjustment needed.
I have only ever broken one die, and that wasn't long ago either. I was cutting an oversized thread to fit a worn hole, and bored out the holder so that I could expand the die a bit further, I cut the thread perfectly, but when I took the die out of the holder, it was broken in the same place as yours.
Welcome to the club.
If what you did is still not up to standard, bring the bit along next week and we will fix it.
Bogs the builder