The Asarkar whistles, from India, are cyllindrical brass, with a metal block, and a squared windway. They resemble the pictures I’ve seen of Hohner whistles. People frequently come across these in import shops, at eBay, and from various online dealers.
This isn’t really a review, just a few thoughts on them. I have a complete set of the available keys.
They really aren’t bad whistles, but, with the possible exception of the low D (I like the Asarkar low D, it has a great metallic sound), they are sharp of A:440, so not the first choice for playing with other instruments, as they are one-piece, and quite nontunable. But, at around US$8, the low G whistle is worth it, I think.
I’ve posted clips of the lower-key ones in the past, and have a new clip of the high D at Clips & Snips. http://www.tinwhistletunes.com/clipssnip/Audio/4-03/travlingAaronW.mp3
As can be seen in the clip, this high D was demonstrating an inconsistent breathiness.