When you try the Ilford paper the test is easy. Just apply filters 1-5 to the print. You will either find that each print shows a different contrast in which case Hurrah or you will find that the prints will not respond fully to each successive grade and will print alike and run out of contrast.

If the paper responds as it should between grades 2-3.5 then unless the negs haven't been exposed or developed as they should be and will need rescuing at say grade 4-5 but won't print as they should at these grades then you know that there is some loss of contrast.

Even grey prints i.e. not showing full blacks or bright whites can look OK sometimes in my opinion.