An altar society or altar guild is a group of laypersons in a parish church who maintain the ceremonial objects used in worship.
The duties of members vary according to circumstances, in some instances including those which ordinarily fall within the sacristan's province, such as the vestments and altar vessels and making ready for the Mass.
They would either organise a fund for the maintenance and repair of church vessels or work to maintain the vessels. Altar societies differ from tabernacle societies in that altar societies work for the benefit of the church to which they are attached and tabernacle societies work for the benefit of many different poor churches.
References
Altar society Wikipedia(Text) CC BY-SA