The scroll was of papyrus or leather.
Pieces of fragile papyrus about 10 inches wide were pasted together to make a long roll.
The Old Testament was written on these rolls.
It was a painful labor to copy without errors the rolls, therefore a very costly and precious piece.
One sroll contained a part of the Old Testament book.
The complete Old Testament was kept in the synagogue.
And on the Sabbath, a roll was requested to read from (Luke 4:16-20).
Normally only on the inside was written.
Here in Revelation the roll was written on the inside as well as the outside and sealed with seven seals.
A scroll written on the inside and outside was called an opishograph, representing the fullness of the divine foreknowledge and counsels.
History will not end until God's purposes has fully consummated.