Next time your out metal detecting and you dig a large piece of lead, before you condemn it to the scrap bucket make sure you check it out as it could well be a Palm Guard like these four pictured.
They are mainly circa 18th - 19th century and were used by leather workers. Normally they used to wrap the guard in a cloth, or held in a pouch and used to force needles through the tough material while protecting the users palm. Several impressions from needle-ends are evident.
I have dug these four shown from various pasture sites. They usually have one flat surface and a convex with two indentations.