How do l recondition an old saddlebag that was left wet for ages?

I found a couple ideas for you GG

https://www.youtube.com/watch?v=JF42OdxcFYE

https://www.youtube.com/watch?v=kO84jg7WVhg

I think after thoroughly cleaning it that saddle soap will be your best bet: https://animals.mom.com/how-to-clean-repair-old-saddles-12401816.html

You can purchase a good leather conditioner and cleaner. Automotive stores have very good products and if you think about, leather seats in a car take a lot of abuse. Clean and condition it, making sure you "stuff" it so that it will have a good shape.

How to Restore Leather

https://www.wikihow.com/Restore-Leather

Saddle soap to clean it and leather conditioner to keep it soft and supple.

• I have used Saddle soap for many years on boots, purses etc. After using the soap and cleaning it off . Let the saddle bag dry outside in the sun for a few hours.Then apply a leather repair compound. Using a sponge, gently spread a thin layer of leather binder (a liquid that seeps into the leather fibres and binds them together) over the entire surface of the worn leather. Let it air dry. Repeat the process 3-5 times, or until you are satisfied with the results. Remove excess binder that might accumulate around the seams. Apply a thin coat of colorant. Add a small amount of water-based leather colorant to a sponge or foam applicator. Apply a thin coat onto the leather, concentrating on hard to reach areas like creases, cracks, and seams. Wait 30 minutes for the colorant to dry.Shake the colorant well to ensure that it is mixed well before using it. apply a leather conditioner. Once the leather is dry, use a soft, lint-free cloth to apply a leather conditioner to the surface. Be sure to apply the conditioner evenly and cover the entire surface. Gently buff and polish the leather to make it supple and shiny

You can purchase this in an automotive store look for the kit that restores leather seats.

I found this video which may help: https://www.youtube.com/watch?v=JF42OdxcFYE

We have an old fashioned shoe repair shop in our town. They specialize in leatherwork. I think with a piece this old and sentimental, you might consult a pro. Maybe a dry cleaner could recommend someone?