These pots were produced by Yixing Factory 1 during the 1977-1982 'Green Label' period. They were stored by a collector since then.
The teapots has red clay (Hong Ni) outside and purple clay (Zi Ni) inside, commonly called "Wai Hong Nei Zi" pot. It's a typical shui ping style from Yixing Factory 1 in that period.
The clay used by Factory 1 during this period was very good and these pots are nicely high fired which are well suited for brewing young and aged oolong, and all types of aged teas. Inside has a single hole filter, the wall is medium thickness, the lid is a little loose. We have several of these pots. they are very similar, but may have small differences.