Slick as a whistle

"Slick as a whistle" Yes, this is an old saying that popped up in my head today after saying watch out for the ice - the sidewalk is "slick as a whistle" Maybe the correct saying is "As slick as a whistle. Please help!

I don't know that one. "Clean as a whistle" is at
www.phrases.org.uk bulletin_board 33 messages 522.html