Yup, Enhanced Series is Colt's term for firearms with the Larry Robbins' four-way fire control selector, as opposed to the earlier Sturtevant selector used on the RO605B, RO606B, and RO610B CAR-15s. There's a RO708 M16A2, RO738 M4 Commando Enhanced, a RO748 M162 HBAR Enhanced, a RO778 M4 Enhanced, a R0908 M16A4 Enhanced, a RO938 M4 Commando HBAR, and a RO978 M4 Enhanced. The RO738 M4 Commando Enhanced has an A2-style upper receiver. Here's an image of one that was posted earlier.
There's a picture of a RO978 on page 143 of the Black Rifle and it's stamped "M4 Enhanced".
The gas-piston RO703 also used a Sturtevant four-way selector. The lower receiver has to be made to use to the Robbins device. The Sturtvevant is a drop-in device.
The only organization to purchase the Enhanced series in numbers was the Greek military. Notice the four-way selector on the carbine with the sitting soldier in glasses. Unfortunately, it's currently set on semi.