Peterson made clay pipes during the Patent Era with two shapes being depicted as can be seen in their 1905 Patent Pipe catalogue. It shows shape numbers 8A and 12A. During this period their clay pipes were stamped “Peterson Patent” and could be purchased with either a silver or nickel band. During the second World War, Peterson again started making clay pipes, due to the shortage of briar. The clays of this period are stamped “Peterson System” and were only offered with nickel bands. They continued making their clays until their London shop finally closed in the 1960s. Examples of which can be seen on page 9 of the 1962 &1965 catalogues, priced seven shillings and six pence!!.As to why they are few in number,I suspect that the brittle nature of the clay meant that mortalities would be high.
The photo below shows a recent acquisition, an early Patent glazed shape 8A bent Clay system in remarkably good condition.