Paul:
The top cartridge is the earlier type of round with a 'flat-nosed' projectile for safe use in the Lebel Rifle's tubular magazine; this particular cartridge was manufactured by Kynoch in England.

The 'letter-opener' was made from a 'Balle D' round, made in 1916. The base of the 'Balle D' cartridge has a circular groove surrounding the primer. This prevents spitzer bullet tips from contacting cartridge primers in the Lebel tubular magazine.

The bottom cartridge is post WW-1 and requires arms to have an altered chamber for a larger diameter case-neck.  It can be used in arms stamped with a large "N" on the receiver-ring.