They officially released the details about the extension and the 20% off:

"SALE EXTENDED WITH SPECIAL OFFER:

SAVE 20% OFF THAT ONE ITEM YOU REALLY WANTED: 8 HOURS ONLY

As a special incentive for being a loyal All-Clad fan in 2017 we would like to thank you with an extra 20% off one item only. Add that extra special item to your All-Clad collection now or purchase it for that special someone in your life. For 8-hours only it’s yours for an additional 20% off already amazing prices. Also we are throwing in free shipping on this one item as well. Please see rules to participate.

The additional 20% off is on one item only from 9 AM ET until 5 PM ET on 11/09/2017. You can ONLY have the one item in your cart at checkout for the discount to apply. Use promo code THANKYOU20 at checkout to receive the 20% off. THANKYOU20 promo code is only valid on product from 9 AM ET until 5 PM ET on 11/09/2017 and CANNOT be applied to any past orders. All sales are final and orders CANNOT be canceled including previously placed orders.

PASSCODE TO ENTER THE SITE - THANKYOU20"