I posted this in Off Course but haven't gotten any responses yet.
We are in a "finders keepers losers weepers" situation with a saddle that was deliberately left behind by a former boarder at our barn. Apparently she didn't like it because it tipped her forward. I assume that it probably was too wide for her horse, because the flap is stamped as a 35cm tree. It is an all purpose model with a dressage style flap.
We are looking at it for the 14-year old who is part leasing my horse. It appears to fit both of them at least initially. She is carefully cleaning up months of mold and dirt. It seems to be in very nice condition, including the billets.
I wasn't able to find much searching here and on google regarding Sommer saddles. What I did find pertained to dressage saddles. It looks like a high quality German-made saddle.
Not much help other than to say that I absolutely adore my Sommer saddle. I was introduced to it by a german coach and searched far and wide to find one of my own. Mine is older and I have been told that they changed dramatically at one point with the changing of saddle makers - it's been too long for me to remember names.
I have been lucky that mine has fit a wide variety of horses. I love how much contact it gives you with the horse. That being said, the girl I bought it from hated it because she felt there wasn't enough support for her.