Russell, yes the lid is marked... RB 2778.
PS... I think if I dug around a bit it is likely that they may have used the lid/pattern for the Round Bottom Pot when they made the Franklin Bean Pot.
While the Round Bottom Pot is not shown in 1966, it did 'appear' in the early 1970's.... Still have a large gap in catalogs from 1954 to 1966....
Very few folks realize that even the Round Bottom POT appears to be a newer item, 60's/70's....
During the Red Mountain eras they were called "Straight" pots with very different bail ears shown.