"Cachet" as the printed design is known by cover collectors.
Morris W. Beck covers are known for their high quality color cachets.
Beck is most famous for his series of 1000 covers. The space
recovery covers of that series are of particular interest to collectors
around the world.
He did not use a numbering system on all covers he produced. In
total he produced over 2,000 Event, Naval, Space, and First Day Covers.