I purchased this seat at Hershey this year. The seller described it as a "1600 Carrera seat". I looked at it carefully to see if it was aluminum or steel, I thought all the GT seats were aluminum, this one was steel. The seat is looks like it has the original vinyl, with basket weave centers, and has perlon on the back and sides, it has horse hair padding. Its mounted on a steel hinging/ sliding base allowing it to tilt forward and is adjustable forward and back.
Page 66 of Bret Johnsons book "The 911&912 Porsche"
Describes Sport seat options: "[For 1965 and 1966 there were two alternatives designated as "Recaro" and "Ferrari"] [ The Ferrari seat bore more than a little resemblance to the Speedster seat of the 1950s]
http://www.racecar.co.uk/edmondharri...?ProductID=105
"Original Carrera Abarth & 356 GT seat
Fitted to the B GT and Carrera Abarth, I cannot tell you just how rare this seat is(differs slightly from speedster seat and with more support) in absolutely superb original condition with original material cover and horse hair padding. Black vinyl / cord. Perfect seat for the perfect car. You will never find another !"
The pictures in Brett Johnsons book and on the edmond Harris site look identical.
last picture is the Harris seat
I think this is the same seat used in late 356 Carreras and very early 911s.