Vince, testing hardness is always a matter of comparing. So when you take a (small) steel ball and put it between 2 lead (bullets) in a bench-vice (or whatever that helps you put pressure on it)... the lead with the smallest mark is the hardest.

When you're not rich it helps to be clever

Instead of that bench-vice you could also use 2 screws and 1 nut or even a blow of a hammer. When you want to make it sophisticated you can give that blow with somekind of springdevice which will help you to give rather constant blows and compare results of different measurements.
So a blow job can help to discover the hardness...

There is chart out there to measure hardness using pencils...

Interesting. Fortunately my mate has a cheap hardness tester (bought online for around AUD$120). But if the pencil testing procedure interests you, here is a Google link to the info:

Testing hardness using a pencil