You could ask the person you bought it from what he used the lead
for, altho your hammering needs may well be and most probably are
completey different to his.
Be that as it may, hammering is a very broad term, for example if
you want to turn round wire into thin strip you need a hard hammer
and a hard as in a hard hammer steel block to hammer your wire
between. also they need to be polished with some 600 grit wet and dry
silicon carbide waterproof car body rubbing paper, otherwise any
marks on the hammer or block will show up on the strip.
For repousse work lead will work, try some 1/32 in thick fully
annealed copper sheet on it. always test your techniques on a base
metal befor picking up the expensive stuff.
As for getting pitch, you might try and find a road resurfacing co
near you. they will have access to ashfalt in block form. Similar
Comes from Trinidad. When mixed with sand and stone chippings its
the basis of road surfacing.
You will get it before these are added.
Needs must the devil drives!