Lets see if I can add to the confusion.
Ruger used three frame sizes in the 1950s. The single six, the 357 Blackhawk and the 44 Blackhawk. The Super Blackhawk introduced in 1959 used the 44 Blackhawk frame with changes to the top strap as to accomodate the new sight with protective ears, the 44 Blackhawk was the first large frame, the 44 Blackhawk was produced from 1956 until 1962.
In 1973 the mid size frame on the 357 was dropped. Since 1974 all New Model Blackhawks and New Model Super Blackhawks have used the same large frame with the exception of the 357 Maximum which was produced from 1982 thru 1984. (it was a large frame stretched in length)
The New Vaquero (not New Model) which was introduced in 2005 is on the mid size frame of the 50s and 60s as is the 50th anniversary 357 Blackhawk.
I would suspect the 50th Anniversary 44 Blackhawk will be on the frame of the original Flat Top 44 Blackhawk, as testing in the 1950s proved the mid size frame wouldn't work with the 44 mag. All prototypes failed. That is why the 44 Blackhawk frame (large) came to be.