I suggest reading the following article written by our whistle king, Dale himself. Very, very helpful.
What the heck is the deal on Davy Spillane’s whistles?
A few years ago, Davy, whose email from yours truly he’s either never seen or never answered, abruptly emailed me to say that somewhere on Chiff & Fipple was an indication that he played Overtons or Chieftains or something and, his email went on to say, the truth is that he makes his own instruments and always had. Cease and desist, yada-yada. In addition, his own website included a whole section about Davy offering for sale his own whistles, which I think he called "D500’ or something like that. Should be end of story, right?
Well, maybe it is. But I must point this out: I’m not sure that anyone on the planet has received more whistle related email than I have. In these five-plus years, not ONE PERSON has indicated to me that they have (a) purchased Davy’s whistles, (/) played Davy’s whistles, or (c) seen one up close enough to describe it.
Now, there’s no reason to believe that Davy is lying about making his instruments. So, I assume that he does and that he has sold whistles to very few players because his touring / recording schedule doesn’t allow enough time to make many instruments for others.
Personally, from the picture, it does look like Overton. But again a skilled craftsman can make a whistle which resembles Overton. Who knows? I’m yet confused. I suppose that the if the structure of his whistle is strikingly similar to that of Overton, then it follows that the playability and intonation will come close to Overton whistles.
Source:
Wisely. Undisputed King Dale, “Unsolved Mysteries”, in Chiff and Fipple, [u]http://www.chiffandfipple.com/mysteries/mysteries.htm[/u], retrieved from the World Wide Web, 20/9/2003