I read where you said you are likely to need to change/replace some leather valves. With that in mind I offer you the following to think about,
People should also be aware that this concertina reed pan is a good example of the corrosive effects of alum tanned (naturally white ) valves. While it has good valve properties, they are corrosive to the metal they are near. You can see on the larger reeds where the brass is still bright below the valve, but with progressively more dark patina next to the valves.
The leather valves on my French Accordion are white (now I wonder if they are Alum tanned), so I will look further on what corrosion, if any, is on my reeds.
I had planned replacing with like for like leather; however now I am not sure, based on following the data mentioned by Paul S. Storch
Please also see my article here "starting to repair my French Accordion.
In the following link, Paul S. Storch in a article 'Caring for musical instrument part 1 and 2" from the Minneosota Historical Interpreter, talks about various materials from the early instruments.
One comment he makes in the article is :-
Leather is used in various forms and preparations on both European and non-European instruments. To make it durable and moisture resistant, raw hides to be used for instrument construction must be treated with chemicals known as tanning agents. Vegetable tanning is used where flexibility and water resistance are required. Mineral tanning agents such as alum impart durability but do not have great water resistance. Their use also results in lighter surface colors. Organ bellows, bagpipe bladders and other instrument components of European manufacture are generally made from vegetable-tanned or combination-tanned cowhide or goatskin."