Det Stavangerske Dampskibsselskap AS (DSD) is a private Norwegian transport and shipping company, established in 1855 with headquarters in Stavanger, Norway.

On Tuesday 30 October 1855, the ship named "Ryfylke" came to Stavanger, with its captain Johan Gjemre on the bridge.

Revenue from mail freight eased the burden, but at the general meeting in 1858, proposals were made for the dissolution of the company.

A decision in the Norwegian Parliament Stortinget on state subsidies for private steamship was a turning point.

The company's employees were invited to make suggestions for a flag and a draft designed by chief mate Ommund Thingbø won.

It is unclear where Thingbø picked up the idea, but the base was the three red rings that were painted around the chimneys of all the ships that Det Stavangerske Dampskibsselskap operated.

At two occasions, Puerto Rico has formally requested Det Stavangerske Dampskibsselskap to get the company to change the flag, the first time through the Norwegian Ministry of Foreign Affairs during the 1950s.

Puerto Rico is also not an independent and sovereign state, and their flag can only be hoisted on official buildings along with the American Stars and Stripes.