Norman E. Muller, Conservator of the Art Museum, Princeton University, wrote the technical section on the reconstruction of a mid-fourteenth century altarpiece on which two painters, Bartolommeo Bulgarini and the master of the Palazzo Venezia, apparently collaborated. The only available choice of paintings representing the documented and required subjects is a Nativity-Adoration of the Shepherds at the Fogg Art Museum and two standing saints, St. Victor and St. Corona in the Statens Museum, Copenhagen. The usual criteria, size, shape, molding design, and halo tooling are of limited value because of the fragmentary condition. Yet, despite the loss of the original verso of the Fogg painting due to its transfer onto another support, the evidence of the common construction can be found on the x-rays taken before the transfer. A series of nail holes corresponds with the indication of original joinery, horizontal reinforcing patterns. Their construction must have been the same as on the rear of St. Ansanus (Annunciation) altarpiece of 1333 by Simone Martini, also for the cathedral. The interpretation of the reinforcing structure also permits plotting the original size of the altarpiece. Despite severe damage and restoration of the Fogg tooled patterns, some coincidence with the Copenhagen panels can be established, as the chart of the punch shapes shows. -- AATA