Out of context, and without contexualizing:

1) Asserts that there was a time in the past when Jean, who did not see the letters in question, would have had some enjoyment from seeing them. The enjoyment referred may be having pleasure or some other use.

2) Asserts that there was a time when Jean, who had not *then* seen the letters, would have had pleasure from the fact of having, indeed, seen them.

Now, why do I feel like this is a trap?