Found this clip on youtube from 1996 Davy plays whistle and Uilleann pipes with Mary Black and Emmylou Harris at 1 minute 16 seconds you get a good shot of the whistle which looks like an Bernhard Overton.
http://www.youtube.com/watch?v=Br55Mjve33Q
sponge 
I emailed Davy this note:
Dear Mr. Spillane,
I recently saw a low D whistle on ebay. It is all
aluminum (it does not have a plastic head). The
seller claims this whistle was made by you and
played
by you for Riverdance. Can you confirm or deny the
seller’s claim. Thankyou for any information you
can
give about this whistle.
(I also added the link to the item.)
And recieved this reply:
I ONLY MAKE / HAVE MADE ALL METAL LOW D WHISTLES FOR
MYSELF–NOT FOR SALE
Interesting. I seriously doubt the authenticity of the ebay whistle.
Nice work gallant_murray,
I would say thats as conclusive as you can get, unfortunate for the ebay seller as it seems he was sold it with misleading information from where ever he bought it in ireland, I did recieve an e-mail from the seller and as far as he can remember it was bought directly from Davy Spillane, he cannot locate the invoice and said that he was also issued with an autograph of Davys as well, I suppose a bit like an Overton certificate,
I shall pass on the message from davy as I dont think he has had any luck in contacting him.
sponge
No surprise there.
The seller on Ebay now has the following disclaimer in the ad:
"Dear Ebay User’s,
It is very important that you read this information!!!
Over the last few day’s there has been some discussion & some very welcome research carried out by people who know alot more about this item than I do. It has been brought to my attention that this item was NOT directly made or handmade by Davy Spillane himself. He has only ever made instruments of this kind for himself and not for sale!"
So he’s practicing truth in advertising, if a bit after the fact.
As for whether a real Davy Spillane exists, Fox Mulder said it best: The Truth is Out There.