"The Green Swallow is a Limited Edition of the Swallow Classic, normally sold only in the traditional Brooks colours (black, brown and honey). The 100 pieces are sold in cooperation with the Bicycle Film Festival in NY (May 28-June 1). For each sold saddle BROOKS will devolve 100 $ to support the Bicycle Film Festival.The Swallow reproduces the timeless design of the daddy of all modern racing saddles, first in production in 1937. This limited edition features the original chrome plated steel metalwork. The tensioning plate on the underside still bares the original patenting information retaining the word DEPOSÉ, as the patent for this model was first registered in Paris. Back then many of Brooks saddles in fact were exported to the continent for the use of racers in the tours."
Read more here.
If you're interested in seeing how Brooks saddles are made, check out a nice Flash based factory tour on their homepage menu. This will give you an idea of the manufacturing processes involved.