Firstly, could we establish what we are talking about here.

If they are 78s, they are much more likely to be made of the highly-breakable shellac rather than vinyl.

However, there are also quite a number of early 10" vinyl LPs (33rpm).

The name of the person and the email address that I am sending you in a PM is one of the most knowledgable people in the UK on the release dates, value, packaging etc. of early jazz and blues on 78rpm discs. He is also an avid collector and would probably be looking to fill some of the (few) holes in his huge collection by buying any that you would like to sell