What does this possibly Catholic symbol mean?

This is an amulet of Latin American religions with African roots. It may be Exu trident, Ogun sword, Xango ax and "Tranca rua" key

Having read Ken Graham's answer with examples, I would slightly modify my answer to include the comment that various religions borrow symbols and practices (syncretism). In this case, if the piece has Santeria elements, they are but borrowings from Christianity. At the same time, there is a fairly well-known assimilation with elements of Catholicism. So, while my answer relies on the Bible for its interpretation, this is only to say that some religions modify these things to their own ends. For Christians, it is Christ that holds the key; for others, it may be someone else.

It would appear that the whole piece is referring to Christ Jesus.

Key (singular) refers to the key of David (Rev 3:7), rather than the keys (plural) to the kingdom given to Peter (Mt 16:19). The other parts of the key and objects further show this. The three indents representing the Trinity. The cross by the teeth of the key representing the only way to open the door (in other words, many keys have teeth, but this one has a cross through it). Again, showing Christ as the way, truth, life (Jn 14:6).

The sword represents the double-edged sword that is Christ's (Rev 1:16, 2:12).

The trident top part is to see that on Him (from the hole) hangs all the Law and Prophets (two arms). As well, see Mt 22:37-40, showing the heart, soul, mind. The bottom part represents the Trinity and the power of Christ to calm storms (Isa 17:12, Psalm 107:29, Jon 1:15, Mk 4:39).

The double-edged battle axe represents the LORD of hosts by whom the nations and kingdoms are overcome (Jer 51:19-20).

Basically, it is a representation of Christ and the Great Commission empowerment (Mt 28:18-20)

What does this possibly Catholic symbol mean?

I believe this to be a sort of pantheon of symbols of the Santería culture as practiced by certain individuals living in the Americas. It seems most certainly to be of Santería symbolism(s).

Right from the beginning of this question being asked (Apr 11, 2014, see my comment) I was convinced that this image was anything but Catholic. In fact I am even more convinced that these symbols are more closely related to the religion of Santería. Santería practitioners after all improvise their beliefs with Catholic saints and symbolisms (synchronism), but are in no way Christian in their beliefs, but are more in line with the occult and even possibly Satanism.

Santería, also known as Regla de Ocha, Regla Lucumí, or Lucumí, is an African diasporic religion that developed in Cuba during the late 19th century. It arose through a process of syncretism between the traditional Yoruba religion of West Africa, the Roman Catholic form of Christianity, and Spiritism. There is no central authority in control of Santería and much diversity exists among practitioners, who are known as creyentes ("believers").

Santería is polytheistic and revolves around deities called oricha. Deriving their names and attributes from traditional Yoruba divinities, they are equated with Roman Catholic saints. Each human is believed to have a personal link to a particular oricha who influences their personality. Various myths are told about these oricha, who are regarded as subservient to Olodumare, a transcendent creator deity. Olodumare is believed to be the ultimate source of aché, a supernatural force permeating the universe that can be manipulated through ritual actions. Practitioners venerate the oricha at altars, either in the home or in the casa (temple), which is run by a santero (priest) or santera (priestess). Membership of the casa requires initiation. Offerings to the oricha include fruit, liquor, flowers and sacrificed animals. A central ritual is the toque de santo, in which practitioners drum, sing, and dance to encourage an oricha to possess one of their members and thus communicate with them. Several forms of divination are used, including Ifá, to decipher messages from the oricha. Offerings are also given to the spirits of the dead, with some practitioners identifying as spirit mediums. Healing rituals and the preparation of herbal remedies and talismans also play a prominent role.

Santería developed among Afro-Cuban communities following the Atlantic slave trade of the 16th to 19th centuries. It formed through the blending of the traditional religions brought to Cuba by enslaved West Africans, the majority of them Yoruba, and Roman Catholicism, the only religion legally permitted on the island by the Spanish colonial government. In urban areas of West Cuba, these traditions merged with Spiritist ideas to form the earliest casas during the late 19th century. After the Cuban War of Independence resulted in an independent republic in 1898, its new constitution enshrined freedom of religion. Santería nevertheless remained marginalized by Cuba's Roman Catholic, Euro-Cuban establishment, which typically viewed it as brujería (witchcraft). In the 1960s, growing emigration following the Cuban Revolution spread Santería abroad. The late 20th century saw growing links between Santería and related traditions in West Africa and the Americas, such as Haitian Vodou and Brazilian Candomblé. Since the late 20th century, some practitioners have emphasized a "Yorubization" process to remove Roman Catholic influences and created forms of Santería closer to traditional Yoruba religion.

Practitioners of Santería are primarily found in Cuba's La Habana and Matanzas provinces, although communities exist across the island and abroad, especially among the Cuban diasporas of Mexico and the United States. The religion remains most common among working-class Afro-Cuban communities although is also practiced by individuals of other class and ethnic backgrounds. The number of initiates is estimated to be in the high hundreds of thousands. These initiates serve as diviners and healers for a much larger range of adherents of varying levels of fidelity, making the precise numbers of those involved in Santería difficult to determine. Many of those involved also identify as practitioners of another religion, typically Roman Catholicism.

Exu Trident

Xangô Axe

Shango, also known as Changó or Xangô in Latin America; and as Jakuta or Badé) is an Orisha, a deity in Yoruba religion. Genealogically speaking, Shango is a royal ancestor of the Yoruba as he was the third Alaafin of the Oyo Kingdom prior to his posthumous deification. Shango has numerous manifestations, including Airá, Agodo, Afonja, Lubé, and Obomin. He is known for his powerful double axe (Oṣè). He is considered to be one of the most powerful rulers that Yorubaland has ever produced.

Ṣàngó is venerated in Santería as "Changó". As in the Yoruba religion, Changó is one of the most feared gods in Santería.

In Haïti, he is from the "Nago" Nation, and is known as Ogou Chango. Palo recognizes him as "Siete Rayos".

Ogun Sword or Knife

Ogun or Ogoun is a spirit that appears in several African religions. He attempted to seize the throne after the demise of Obatala, who reigned twice, before and after Oduduwa, but was ousted by Obamakin (Obalufon Ogbogbodirin) and sent on an exile - an event that serves as the core of the Olojo Festival. Ogun was a warrior and a powerful spirit of metal work,13 as well as of rum and rum-making. He is also known as the "god of iron" and is present in Yoruba religion, Haitian Vodou, and West African Vodun.

Symbols

The primary symbols of Ogun are iron, the dog, and the palm frond. They symbolize Ogun's role in transformation, mediation, and function. Iron is the primary emblem of Ogun. Ogun altars and ceremonies display and use iron objects both in Yoruba areas and across the African diaspora. Followers of Ogun wear chains of iron implements; Ogun festivals feature the display of knives, guns, blacksmith implements, scissors, wrenches, and other iron implements from daily life.

What does the symbol of the key mean?

Keys have represented various spiritual symbologies for as long as man has had locks. They are connected with gateways and portals, doorways to the unknown, knowledge, mysteries, powers, initiations, new ways, forbidden things and answers to curious questions. They are often associated with various literary idioms, specific deities or spiritual figures, and are often used as part of charms or other magical tools. We in modern times still value keys as an important part of our daily lives, such as car keys and house keys, however with digital locks, passwords, and other technological advances, it is interesting to speculate if the key will continue to play as significant role as a tool as it has in the past. Yes, there will always be some types of keys as in pass codes or other devices, but the idea of having a piece of metal cut to a specific shape, I fear is losing it’s place in the world of the future. However, in the magical realm and the world of witchcraft and hoodoo, the key still has a role to play and is commonly found in most crafter’s tool kit.

First let’s look at some spiritual figures that are most often associated with keys. In Christianity, the visage of Saint Peter holding the keys to the gates of Heaven can be easily found in religious art from Christendom to the modern era. He is often portrayed with two keys; a golden key, representing the power to allow those who are worthy to enter into eternal life, the other a silver or iron key to close them again. Keys also represent spiritual purity and enlightenment in these scenes. He is one of the most familiar figures in religious realms to represent a gatekeeper allowing others to pass into the spiritual realm; however, he is not alone in this task.

In Voodoo practices, Papa Legba, often depicted as an elderly man with a cane, a dog and keys is also a gatekeeper, acting as a liaison for those between the spiritual and the physical realms. He is said to speak every Human language and be a conduit between the mortal and deities, allowing for communion and safe passage if travel into the astral planes is granted. - The Symbolic Meaning of Keys

I believe these are symbols of martyred apostles.

• Key: Peter
• Sword: Paul
• Axe: Possibly Matthew
• Trident: Thomas

Jacob Prahlow has collected some research.

Although an upside-down cross is associated with Peter, he was given the keys of the kingdom (Cf. Matthew 16:19) and the key is a very common symbol.

Paul, a Roman citizen, was executed by the sword rather than crucified. While the date of his death is rather hazy, the place is known and there is an enormous basilica on the site. Paul is very often depicted with one or two swords: the sword of truth and the sword of martyrdom.

Both Matthew and James brother of John are traditionally held to have been martyred by beheading. James is recorded in Acts 12 as being killed “by the sword” — Matthew’s death is not recorded, but one tradition is that he died by the axe.

One legend of Thomas’ death in India is that he was killed with a trident.