Some info about it:
Agnus Dei
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"An Agnus Dei (the name means, of course, “lamb of God,” and is pronounced “ah-nyoos day-ee”) is a round or oval wax disk impressed, most often, with the figure of a lamb, but sometimes with a flag, figure of a Saint, or the papal arms, etc. They were blessed and distributed by Popes in the first year of their pontificates, and then every 7 years thereafter, on Holy Saturday. After the “Agnus Dei” at the Mass that day, the Pope would place a packet of them into the mitres of the Bishops present, who would then distribute them themselves.
They are very ancient, being first mentioned ca. A.D. 820 – possibly earlier if the mention of blessing wax in by Pope Zosimus in the
Liber Pontificales in A.D. 418 refer to Agnus Dei – and it is believed that the first ones were made of leftover wax from the Paschal candle mixed with chrism. More recently, they’d be dipped in water mixed with chrism after being formed, and then sewn into small pouches of various shapes to keep them clean and safe.
The symbolism of the Agnus Dei is the same as that of the Paschal Candle; the wax is the pure flesh of Christ, and their protective qualities are like those of other blessed objects, with the Pope’s blessing mentioning specifically protection in combat, and protection against tempests, lightning, fire and water; malice of demons and of every adversity; pentilence, sickness, and a sudden and unprovided death.
Popes, unfortunately, no longer bless and distribute Agnus Dei. At any rate, any Agnus Dei you come across (that is genuine) will date to before 1964, the year “modern man” apparently came into being. You should keep it very safe."
