A group of 17 paintings made on oak panels, from an original polyptych of the altarpiece of the Cathedral of Évora, Portugal.
Date: The polyptych is dated from early 16th century.
Author: unknown, but probably an ecletic group of Flemish painting masters.

General Composition:

13 vertical rectangular panels - Scenes of the Life of the Virgin;
6 Predellas - Scenes of the Passion of Jesus.

Composition of the Scenes of the Life of the Virgin:
Identification of the scenes:
1 - Saint Anne and Saint Joaquim; 
2  - Birth of the Virgin; 
3 - Presentation of the Virgin in the Temple; 
4 - Wedding of the Virgin; 
5 - Annunciation; 
6 - Manger; 
7 - Adoration of the Kings; 
8 - Escape to Egypt; 
9 - Circumcision of Jesus; 
10 - Presentation of the Child in the Temple; 
11 - The Child Among the Doctors; 
12 - Death of the Virgin; 
13 Coronation of the Virgin.

Dimensions of each panel: Aprox. 190 cm height x 110 cm width x 35 mm thick; Panel 13 is exceptionally larger, with 269 cm x 157 cm x 28 mm.
Picture
Coronation of the Virgin. Dimensions: 269 cm x 157 cm x 28 mm.

Composition of the Scenes of the Passion of Jesus:


1 - The Last Supper; 
2 - The Prison of Christ; 
3 - Christ and Pilates; 
4 - Descent from the Cross; 
5 - Resurrection of Christ.
6 - Ascension of Christ.

Dimensions of each panel: Aprox. 77 cm height x 88  cm width x 35 mm thick.

Next powerpoint shows each panel front side before treatment, followed by a diagram made from the radiography showing the construction technique, enhancing the floating wooden keys in the butt joins (in orange), other smaller wooden keys out in an older restoration treatment ( in green) and the butterfly keys adapted from the back side of the panels ( in outline).

link to video about the temporary exhibition of the set of paintings in the MNAA in Lisbon:
​http://aeiou.expresso.pt/gen.pl?p=stories&op=view&fokey=ex.stories/251357




Small video showing the procedure to replace old "butterfly keys" by new wood pieces with the grain in the same direction of the painted boards. 
Butterfly keys were commonly introduced in the backs of the panel paintings, as part of the original construction or as part of structural restoration, and  always with the purpose of reinforcement elements of the joins, but it was noted throughout the ages that this type of elements create problems to the movement of the wood, and consequently, to the painting. In this case, the joins were firstly re-glued with the add of clamping, and then only after the new pieces are introduced in the sockets of the old butterflies.
Final display of the set in the Museum of Évora, Porugal.