Mold is easy to remove with an ammonia-water solution. What model is it? If you post a picture, we can probably tell you. Most likely it is a Siegfried since this has been Stubben's most popular model for years.
The tree width is usually stamped on the right-hand billet guard under the serial number. The silver buttons often give a clue as to the saddle's age. I am posting a link to help you determine how old it is.
If it is really cheap--like under $100--it might be worth cleaning up for resale. That depends on its condition. You'll have to make sure the tree is sound, and if it is old, it might need new billets--not a cheap repair.
The resale value depends on the model and the appearance of the saddle. Look on ebay and see what they are going for.
I heard a neigh. Oh, such a brisk and melodious neigh as that was! My very heart leaped with delight at the sound. --Nathaniel Hawthorne
Where are the thrift stores you all are shopping at? I sure don't find things like that at mine.
As far as the saddle, look it over good, is the flocking still good, check the tree to see if it's obviously broken, billets still good? If it looks serviceable but just needs a good cleaning and it was dirt cheap you could get it and try to resell it but old used Stubbens are probably not going to make your very much.
Other things to avoid are excessive wear to the seat (it's a very expensive repair) and wear/repairs in the panels.
Mold wouldn't bother me that much but I would want to check to see the panels don't have a lot of cracking and that the stitching isn't too loose. Cleaned up, the saddle is probably worth about $250 so keep that in mind.
As from the SMB? You can find them used for $20 in lots of places. Not an incredible deal. I had a pair that I sold for about that much on eBay and they had only been used a few times.
Originally Posted by buck22
Do your best to be sure the tree isn't broken, the panels not rotted, super hard or falling off, and the billets not dry rotted or coming off.
Would be a real shame to bring it home only to discover its no more good than a paperweight.
And it would be doubly a shame to clean it up and sell it on and a rider or horse gets hurt because there's something wrong with it.