When held by a Pokémon, increases to that Pokémon's friendship are increased by 50% of the change. Soothe Bell's effect applies directly to the original change in friendship.
Generation IV onward
Soothe Bell's effect now applies to the friendship change after including Luxury Ball and met location bonuses.
Soothe Bells appeared in Smells Like Team Spirit! as the prize for winning the Hearthome City Tag Battle Competition; due to being a Tag Battle competition, the prize was two Soothe Bells, one for each winner. Ash and Paul won them; however, Paul did not want his, so Ash is in possession of both. Ash's Soothe Bells made an appearance at the start of In The Shadow of Zekrom!, on Ash's desk along with various other gifts and prizes he received in the Sinnohregion.