Bell in ruined portal chest

first i loaded up the world then found a village that i never went to then i followed a river then found a ruined portal and opened the chest and there was a bell inside i had never seen a bell in a ruined portal chest then i went to load the same seed  on a new world and there was a bell in the ruined portal . so is this a feature or a bug?if it is a bug could it be a feture please?