Some time ago I was lucky to get my hands on a Prussian lead coated shell (top) resembling a "normal" c/73 or c/76 (bottom) with some slight differences: Instead of 20cm, it is 21cm long. The base diameter is 7.1cm instead of 7.5cm and the walls of the shell are not parallel at the base. The whole projectile seems to be "streamlined". On the other hand - the finishing of the projectile is quite crude with large molding seams.
Enjoy!
Enjoy!