I understand you both - the plates are proberly gone bad... Bu as it happens, there are 5 boxes in all (50plates).. So I might open one of them gently, without destroying the box and make a test..

I know our museum of photography here in DK would be interested in getting the emty boxes after use.. and my thought was also this: if they are gone bad - then I could fix them out - let them dry and then apply my own emulsion on them.... (pre-made plates)...

I am not sure anyone would actually pay for this stuff.... (would be rather expensive to ship..)