The story of the works of Erling Christoffersen is also the story about the applied arts center and school PLUS in Fredrikstad, Norway. The idea behind this for Norwegian craftsdesigners so important center founded in 1958, was to establish a design center where designers working with glass, ceramics and textiles were to create good models for the industry. However the center is most well known for the craft products in small or medium-sized editions.

Erling Christoffersen was the leader of the PLUS silver workshop, named Norway Silver Designs, from the start in 1958. He, his wife Anna Greta Eker, and Tone Vigeland were the leading designers of jewelry from the PLUS workshop through the 1960s and until the jewelry production was closed down in mid 1970s.

While Tone Vigeland and Anna Greta Eker had their emphasis on jewelry, Erling Christoffersen had a broader production, also working in larger scale with unique silver corpus pieces, that were ordered from churches and others. He was trained at the Norwegian company J. Tostrup in the late 1940s, and has also studied at National College of Art and Design (NCAD), Oslo.

In addition to jewelry in silver and with stones, a series of rough Plus pewter pendants designed by Erling Christoffersen was issued, inspired by the Saga Age.