A stone cannon ball for coments

[fernando]

This is a "pelouro" quoted to be from the XIV-XV century.
I guess is limestone, but i am not certain; it is not granite, that i can see.
With a diameter of 19 cms (7,5"), it weighs 7,8 Kgs., this is already the caliber of a significant "stoner" cannon.
Assuming its origin is Germany, once i acquired it in a German auctioner (with somebody's help ), its virtual weight should be quoted in Pfund (German for pound), but i ignore its correspondence to the Kilogram that ran in the period ... a span of 410 to 500 grams is possible.
I wonder whether the cavalry is around, to come and save me from all such doubts.