That's what it looks like - a beveled edge.

Ah, interesting thanks

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You can play beautiful music on an ugly flute
My musical endeavours on my blog

I tried to play one of those once and I needed about 20 minutes till it made a sound at all. And I do play the quena. So those rim blown flutes without a nodge are much harder to play.

Good man yourself - it took me about the same time, but with help from a brilliant teacher.
He told me the average time students need to just produce a well-defined tone is between three weeks and three months.