They are ocasions in wich you really have to be as accurate as possible. Especially when it comes to restoration.
Sure they are many options for leather saddles, starting with the very well-known Brooks: http://www.brookssaddles.com/ , the Lepper: http://www.lepper.nl/ , the Cardiff: http://www.cardiffltd.com/ , the Person, and the very interesting Selle An-atomica: http://www.selleanatomica.com/images/Img4172.jpg . But I'm working in an Orbea fom the fifty's and I've been lucky enough to find the right saddle. The only problem was that the poor thing was all cracked and in bad shape but it was still possible to recover. So I, very carefully, removed the leather from the metal structure, washed gently with tepid water and a soft soap, and once dry, I've sanded it with a very fine sandpaper. I could have used liquid leather to refill the holes but they weren't that big so after that I've dyed it with Tarrago dyes: http://www.tarrago.com/
Judge for yourselves!*
*Note: They are other ways maybe, more respectfull, to restore a leather saddle, That's one of the first I've discovered by myself. The post is about three years old and now I know I would have done it differently.
Anyway, may be of help to someone. In the future I'll update the subjet.