Sociedade Irmãos Simões was founded by Joaquim Simões Costa in the early 1950s. The company was acquired by OSP in 1964 and in 1971 production facilities were merged at a factory in Malaposta, Anadia.
In the 1960s they imported Tansini engines from Italy. Dúnia was one of the brands they marketed their machines under.
Many models were built including Hare, Cyclone, V4, TC 50, Re 50, Admiral 4 Sport, Super V5 and V5 Fuego. These were fitted with 50cc Sachs engines which they produced under licence.
S.I.S. exported to the USA in the mid 1960s and were sold by Cycle International of California, and in Switzerland the importer was A. Strasser, 4562 Biberist, Gartenstr. 9.
The factory closed in the mid-1990s.
Sources: Motos de Portugal, mop-ed.se