I have absolutely no idea what the extra bead may be for. Did you inherit the rosary? It could be, as is mentioned above, a bead attached to remind the user of an additional prayer they were accustomed to say. As pianistclare stated above, the M with the cross on the centre-medal is a Marian monogram. In fact it’s the reverse-side of the miraculous medal. The cross, of course is Christ’s cross. The M represents Mary standing at the foot of His Cross, the two hears on each side are the Immaculate Heart of Mary and the Sacred Heart of Jesus, respectively (each have their own imagery you won’t see very well on a small medal). The stars are the 12 stars that represent the 12 tribes of Israel and the 12 apostles.
The rosary takes on many forms and expressions. At its core it is the meditation of the lives of Jesus and Mary whilst reciting the Our Father and the Hail Mary. This is what Our Lady gave to Saint Dominic. It’s likely that the current Dominican rosary faithfully mirrors its original form but it’s also likely not an exact rendition of the original devotion.
The most common forms of the rosary are…
The Dominican Rosary: This is composed of 15 decades with 15 attached mysteries. The 5 Joyful Mysteries, the 5 Sorrowful Mysteries and the 5 Glorious Mysteries. A decade is composed of 1 Our Father and 10 Hail Mary. Saint Louis-Marie de Montfort added the tradition of ending a Glory be to the Father at the end of each decade, and devotion to Our Lady of Fatima added in the “O my Jesus” prayer. This form of the rosary is traditionally opened with an Apostles Creed, an Our Father and three Hail Mary. It is closed with the Salve Regina, versicle, response and collect. Pope Saint John Paul II introduced the Luminous Mysteries, which is a chaplet dedicated to the public ministry of Christ. It’s an option for those that wish to avail themselves of it. I personally prefer the traditional 15 mysteries and their reflection of the 150 Psalms. The Dominican Order’s faithful traditionally opened the rosary with the opening of Matins from the Dominican Use of the Divine Office rather than the Credo, Pater and Ave we are familiar with.
The Brigittine Rosary: This is a form of the rosary that was popular in the northern European regions. It is also, incidentally, the form of the rosary that Our Lady of Lourdes carried, and was also the form popular with the Discalced Carmelites who used to wear it attached to their habits (Saint Teresa of Ávila reportedly having learned it from a local convent of Brigittine nuns). It is substantially the same as the Dominican rosary with a few differences. Each of the five traditional set of mysteries have an additional mystery, bringing their respective totals up to 6, and the rosary as a whole to 18. The 1st Joyful Mysteries is the Immaculate Conception of the Blessed Virgin. The 6th Sorrowful Mystery is the descent of Christ from the Cross into His Mother’s arms, and the 6th Glorious Mystery is the Patronage of the Blessed Virgin for her faithful (and for Carmelites in particular it’s the Patronage Our Lady of Mount Carmel has for her order). Rather than ending with a Glory be to the Father each decade ends with an Apostle’s Creed. So your typical rosary will have 6 Credos! The rosary opens with the versicle and response “O God come to…”, “O Lord, make haste…”. It ends with an Apostle’s Creed, an Our Father and three Hail Mary. This brings the total number of Our Father up to 7, in honour of the seven sorrows and seven joys of Mary, and the total number of Hail Mary to 63, which is the traditional age recognised by Northern Europeans as being the age when Mary died and was assumed into Heaven. This closing Credo, Pater and three Ave found its way to the start of the Dominican rosary we have today.
The Franciscan Crown/The Seraphic Rosary: This is the form of the rosary popular amongst those of the Franciscan family. It was reportedly given to a young friar by Our Lady so that he could continue to honour and reverence her. It is composed of 7 decades and a further 2 Hail Mary, thus bringing the total number of Hail Mary up to 72, to reflect the Franciscan tradition of Mary’s age being 72 at the time of her death. The seven mysteries meditated on in the Franciscan Crown are the seven joys and glories of the Blessed Virgin.
The Servite Rosary/The Chaplet of Our Lady of Sorrows: This is another very popular rosary, which has a strong connection to the Servite Order. There are 7 mysteries, the sorrowful mysteries of the Blessed Virgin, which are meditated on whilst reciting 1 Our Father and 7 Hail Mary per “decade.” There is some variation in the opening and closing prayers and the post-decade prayers. You can go with whatever tickles your fancy, essentially.
In Jesus and Mary,
OS.