https://es.wikipedia.org/wiki/Retablo
El retablo es la estructura arquitectónica, pictórica y escultórica que se sitúa detrás del altar en las iglesias católicas (en las ortodoxas no hay una función semejante, dada la presencia del iconostasio, y en las protestantes suele optarse por una gran reducción de la decoración).

https://en.wikipedia.org/wiki/Reredos
A reredos or raredos is an altarpiece, or a screen or decoration behind the altar in a church, usually depicting religious iconography or images. In French and sometimes in English, this is called a retable; in Catalan a retaule, in Spanish a retablo, etc. It can be made of stone, wood, metal, ivory, or a combination of materials.

Spain Europe Andalusia Church Stock Photos and ... - Alamy
www.alamy.com/stock-photo/spain-europe-andalusia-church.htm...
Cathedral in the town of Jerez de la Frontera, Costa de la Luz, Province of Cadiz, ... Spain, Andalusia, Sevilla, **Gothic retablo (reredos or altarpiece)** from the ...

http://espanafascinante.com/english/things-to-do-in-jerez-de...
Regarding parishes, we highlight Santiago (13th century), San Miguel (15th-16th centuries), San Lucas, San Marcos and San Mateo (which both hold an altarpiece from the 18th century). Some other important parishes and churches are Las Angustias (17th century), La Santísima Trinidad (16th century), ***San Juan de Letrán Church (with an altarpiece from the 18th century)***, and San Juan de los Caballeros Church (15th century).

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https://books.google.com.jm/books?id=QIdYe9lbiKcC&pg=PA59&lp...

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Note added at 7 hrs (2015-12-22 20:11:21 GMT)
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"Retablo" is singular so I would think it refers to one particular altarpiece ("the Altarpiece" in Jerez de la Frontera, but the title does not specify which particular church.

In your context, I would assume it is just one (1) retablo. Retablos is the pl. form.

http://www.worldcat.org/title/retablo-en-jerez-de-la-fronter...
El retablo en Jerez de la Frontera durante el siglo XVIII

Author: José Manuel Moreno Arana
Publisher: Sevilla : Secretariado de Publicaciones de la Universidad de Sevilla, 2014.
Series: Serie Arte, no. 36.
Edition/Format: Print book : Spanish View all editions and formats
Database: WorldCat
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Subjects
Retablos -- Jerez de la Frontera -- S.XVIII
Altarpieces, Spanish -- Spain -- Jerez de la Frontera (Spain)
Altarpieces, Baroque -- Spain -- Jerez de la Frontera (Spain)
View all subjects
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Note added at 7 hrs (2015-12-22 20:53:00 GMT)
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Broca:

What evidence is there that it is more than one altarpiece? The excerpt and specifically the title says "El retablo"? That is why I asked you if it references a particular church? I can't help much more than I have already. I am sorry. Here is one more link: https://www.youtube.com/watch?v=vuca1K6F8wI (in English):
The church of San Dionisio city of Jerez de la Frontera (Andalusia, Spain) is a Catholic parish church built in the second half of the fifteenth century in Gothic-Mudejar style, although altered with baroque transformations in the eighteenth century. It has recently undergone a restoration. The church was built around 1457 in Gothic-Mudejar style, set in Seville on the 1360s, following the guidelines established by those diocesan teachers, where teachers footprint local builders shows. The parish under the invocation of San Dionisio was established by Alfonso X El Sabio after the final conquest of the city in 1264, on the day of San Dionisio, future patron of the city (That despite an error in the saint, was maintained by papal decree). In the eighteenth century it underwent a major transformation in its interior, which adopted Baroque air. Cultural Interest (BIC), this church was declared a National Historic-Artistic Monument in 1964. San Dionisio currently in perfect condition after a thorough restoration that almost reaches one million euros and archaeological remains discovered in the basement that lengthened works. The temple is the canonical headquarters of the Brotherhood of Suffering since its founding in 1414, that procession in Jerez evening of Holy Thursday and owns the footsteps of Lord of Ecce Homo and Our Lady of Suffering. It is a basilica church, divided into three naves by high and clean cruciform pillars adorned with large almohades ties that lead up to the capitals. The arches separating the ships, less facing the altar, are pointed and jagged, running over them a petite polilobulada border. Each of the ships ends in apse, covered by two baroque altarpieces of the XVIII century, being remarkable the Altarpiece, most of it from the old church of the Jesuits. It is known that between 1728 and 1731 the architect Diego Antonio Diaz transforms and barroquiza inside, preserved since few samples of primitive mudejarismo. The works affecting the headwaters of the ships, with his old wooden ceiling was replaced by a vaulted roof. After the Lisbon earthquake of 1755, were performed new works also under the direction of architect Pedro de Silva, between 1758 and 1760, which hit the decks, piers, and bell choir, performed by the Jerez alarife Juan de Vargas. A recent reform has spare interesting coffered wooden beams and multiple details and elements on its original site, while its walls have been cleaned to appear inside the grandeur and splendor that are today. Inwardly, are of great architectural side chapels, baptism and the Christ of Waters, with its arches framed by alfiz polibulados access and vaults, also Mudejar. The image of the Christ of Waters, dated to the late fifteenth century, has a tradition of popular devotion. Another class of value is the image of Our Lady of Suffering, Baroque work of the second half of the seventeenth century. Equally interesting is outside the temple, which clearly shows the Moorish type of the church, with its three facades; two with pointed arch doors and classic flare. The foot also presents a simple front exterior wall finish superiorly peak in the center, reflecting the sloping roof gable with the building tops, and leaves in the center, on the cover of access a simple rosette round also flared. Adjoining the temple is the Torre de la Atalaya, mid-fifteenth century, also called the Clock, the Council and the Vela. It is considered a Cultural independently church.