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.

I'm not too experienced in them but find a properly made one to be a real joy musically. So my only advice is to source an instrument from a maker guaranteed to know what they're doing and be reliable, so that the only challenge is getting used to the instrument, and to never put yourself in the fate of dealing with a faultily-crafted instrument. And to not know the difference can be VERY frustrating!

The mouthpiece area is critically important, the blade design, and the seal that's possible at the end of the tube. The instrument will likely have a sweet spot, where the air flow, if directed properly, will suddenly make a very musical tone, clear and rich. A poorly made one, like one of the rapidly carved out gimmick pieces sold to unsuspecting tourists at music festivals, for a low impulse-buy price, is a risky venture. From there, check the intonation, but if the bamboo or other material is reasonably consistent along its length, then intonation from a skilled crafter, should be acceptable. But test it out if you can. If you can't, buy only from an acknowledged maker of instruments getting consistent good reviews.

That being said, if you ever drop into an importer store in North America and happen to try out some instrument that has a nice character to it, give it a fast test drive. Maybe one of the cheap instruments is a gem and you can walk out with a great little instrument. I've browsed through such stores and played the various instruments. Some types of instrument are more reliably made than others, but still, from instrument to instrument of the same "model", you can have a wide variety of qualities and responses. But there are some gems in such places, and usually the store owner or person traveling the world in search of clothes and gifts and items to fill their store, isn't a keen musician and isn't sharp on detecting which ones are low quality and which ones are far better.

[quote="papageno"][quote="Geoffrey Ellis"]

And in this discussion, let's not omit the shakuhachi, since it another type of rim blown flute.[/quote]

Speaking of the shakuhachi, I decided to try one of those as well. As a total neophyte I didn't feel ready for one of the beauties by Geoffrey Ellis, so I opted for a shakuhachi yuu. Seeing that they are temporarily unavailable in the USA, I purchased one directly from Japan. Ordered on October 17th, shipped the 18th and arrived at my door today the 20th at noon! All for $120.
So far I have successfully but inconsistently produced a tone. I'll be checking out Youtube videos for some instruction.[/quote]

For what it is, the Yuu is a fairly decent shakuhachi. Many players have started on it, and it's great for a beach or car flute. One key to consistent shakuhachi sound is to keep your face relaxed. Your lower lip needs to cover the back part (toward you) of the end of the tube. With the tube end mostly covered with your lower lip, search up and down for the elusive tone. Try to relax your lips. Let a little air into your cheeks. (mostly a relaxation technique) I find it easiest for beginners to close the thumb hole and the top hole on the front for that first sound. (4 and 5, shakuhachi holes are counted from the far end of the instrument). Everybody starts playing flat, as your embouchure improves you'll get more into tune.