Just FYI. My 2 Metuchen cars, 9/11/69 and 9/30/69 (Vermillion and White interiors, both black consoles) have flat lids and My M code car (Dearborn, 1/23/70) has a Ginger interior and also has a flat lid... The first two cars ar e fairly low mileage (59K, 86K) and the Ginger interior car was alot of miles , but I bought it off the original owner in 1986 so I'm almost positive they all have the original parts ....
In my spare parts pile I have 4 extra 70 consoles, Black, 2 Green, and a Blue. all have flat lids...
A friend worked at a Lincoln/mercury dealer in 68-73 and some of my best new mustang take off parts came from him. Apparently it was not uncommon for Cougars to come in with a mustang horn pad or one mustang door panel and they would switch them out at the dealer..
Just some more data points, John