Years ago I got a “Maith” C whistle online. It was cheap (maybe $7 or $8 with shipping) so when it arrived as a pretty poor-playing whistle I just put it in a drawer and forgot about it. It was super-quiet and required a lot of breath control to prevent flipping to the higher octave. But the main problem was poor hole spacing that resulted in a noticeably sharp F (G-fingering on a D whistle).
Here’s how it looked and sounded (it’s painted 1/2" cvpc pipe with a wood fipple and painted copper mouthpiece, Gonzato style):
https://app.box.com/s/lpi9xwvet7tlbaxe0x4a
So the other day out of boredom I decided to hack away at it to see if it could be made into a playable C# whistle. I took a bit off the bell end, widened the holes, and tried to file the ramp a bit as well. I don’t have any machine tools or workspace at the moment, so all I used was a tube cutter, files, and a small carving blade. I am pretty much the opposite of handy and artistic, so it looks like a bit of a massacre, but I did get it pretty playable. It still has a weak bell note.
https://app.box.com/s/jfrpjqcgqyhbo2cbzau4
I don’t need a c# whistle, or the constant reminder of my inartful handiwork. So if anyone wants this, I’ll send it to you free of charge. You may want to do some fine sanding of the rough edges, but it works as is. If not perfectly satisfied, return to the nearest landfill for a full refund. PM me if you are interested.