MD (Machine doubling) from a very worn out die. Notice how the devices are thinning out. On a doubled die you would see a thickening of the devices. Also note that on your second picture for instance, is 'surrounded', that would not happen with doubling.
The Ike Group and Wexler show no DDO and Variety Vista has a minor variety which is nothing like yours. I think if the Ike Group has never seen a DDO variety of a 1976S in 45 years since issue, it is unlikely that you have a new variety. As stated above it seems to be a mixture of MD and DDD
