Can't find this with google and I've long since forgotten. Does anyone remember what the hypothetical coupon on US 10 year futures used to be (now 6%) before 2000? Was it 8%? GAT
Have a look at this page. A PDF document. It talks about CBOT being forced to change the bond coupon rate from 8% to 6% for contracts expiring before March 2000. See note 5 on page 5.