" The Raleigh Optima was the first TIG welded steel frame from Raleigh and was made in Reynolds 501 material (now 525) As this was a TIG welded frame Reynolds made the top and seat tube with special butt profiles to Raleigh design, to suit the TIG welding. Most butt profiles at the time were suitable for lug construction.
The down tube was not butted, it had eight internal flats designed to add stiffness."