I'm guessing the one on the right was never used and just thrown away as a casing (meaning never had a projectile stuck in the end of it). This was found on the bank of a local river, about an inch down, after the river had just recovered from a flood.
The one on the left has a crimpled/pinched end (I'm guessing that makes it a blank?) and was found in the grounds of an old manor house that dates back to the 1300's, about 8 inches down and next to a large tree.
Both found with my shiny new Euro Ace!

Apart from that, any further info would be appreciated.

Cheers
Mark