S&S design #2079.
One version has an extended/traditional counter. (SWAN 50 - S&S #2079.1)
Available as sloop or ketch and taller rig.
Also sold in the US by Palmer Johnson as the PALMER JOHNSON 48/50. (S&S #2079.2 though these yacht were delivered from original builder in ‘sail away’ condition.)
(Dimensions vary slightly from one rendering to another.)
At least one boat was built to this same design, (of teak) by Sangermani of Italy.