There is no direct evidence of the initial steps in the manufacture of PC.B.060. A block of raw material was probably cut and ground, yielding a pre-form that outlined its main elements, including the beak, the top of the head, a protrusion atop the beak to hold a small perforation, and a disk-like core behind the head. For finer definition of volumes, the craftsman probably used cutting, incising, and drilling, the latter evidenced by shallow marks left by thin hollow drill bits of approximately 4.3 mm in diameter visible on the junction between the disk-like core on the back of the head and the lower and upper beaks.
Large holes were bored to define the eyes in a two-step process. The right eye has a concave, polished bottom, suggesting the use of a conical or spherical solid drill bit approximately 1.45 cm in diameter. A second drill using a hollow bit, 1.14 cm in diameter, cut the bottom of the earlier perforation. The perforation for the left eye was first executed with a conical or spherical solid bit 1.4 cm in diameter, followed by a superficial perforation by a hollow drill 3.4 mm in diameter. The second drilling in each eye created uneven surfaces that would have enhanced the adherence of a bonding material used to keep inlays in place. These inlays, together with any adhesive residue, eventually fell off.

The hole in the protuberance above the beak of PC.B.060, 2.7 mm in diameter, has a straight course, suggesting that a single perforation proceeded from either the right or the left side. The piece was also bored from side to side, proceeding from both ends, in the middle of the disk-like core. Perforations that traverse the core do not seem to taper and were done at slightly inclined angles. The superior border of the core is stepped, and the outer band on the anterior surface of the disk has traces of at least three shallow marks left by hollow tubular drill bits. Portions of this band, however, appear to have eroded and then were mended with some kind of paste. Shallow drill bit marks suggest that, before the mending, the outer band may have had originally six shallow perforations. One of these is clean and exhibits clear evidence of the use of a thin tubular hollow drill bit 4 mm in diameter. These perforations must have held inlays, now missing. Slightly affected by ero¬sion, the back surface of the core was originally ground and polished, as was the inferior surface of the eagle head. Scanty traces of a red pigment cover some surfaces, including portions that had been repaired.
The bores that traverse the piece do not seem to be related to suspension. Suspended from a string passed through the main bore, the weight of the piece makes it tilt forward. Although the tilting can be counteracted by fixing a string to the hole in the protuberance above the beak and tying it to the other string, suspension would have required several points of anchorage.

Benson, Elizabeth P. 1963 Handbook of the Robert Woods Bliss Collection of Pre-Columbian Art. Dumbarton Oaks, Trustees for Harvard University, Washington, D.C., p. 29, cat. 147.

Bliss, Robert Woods 1947 Indigenous Art of the Americas: Collection of Robert Woods Bliss. National Gallery of Art, Smithsonian Institution, Washington, D.C., p. 13, cat. 42.

Bliss, Robert W. 1957 Pre-Columbian Art: The Robert Woods Bliss Collection. Text and Critical Analyses by S. K. Lothrop, Joy Mahler and William F. Foshag. Phaidon, New York. p. 239, cat. 43, pl. XXX.

Bliss, Robert W. 1959 Pre-Columbian Art: The Robert Woods Bliss Collection. 2nd ed. Text and Critical Analyses by S. K. Lothrop, Joy Mahler and William F. Foshag. Phaidon, London. p. 247, cat. 43, pl. XXX.

"Indigenous Art of the Americas", National Gallery of Art, Washington DC, April 1947 to July 1949, November 1952 to July 1962.

"Flights of Fancy: Birds in Pre-Columbian Art" Dumbarton Oaks, Washington, DC, 10/1/2009 - 2/28/2010.

Purchased from Earl Stendahl, Los Angeles (dealer), by Robert Woods Bliss, 1943.

Robert Woods Bliss Collection of Pre-Columbian Art, Washington, DC, 1943-1962.

Dumbarton Oaks Research Library and Collection, Pre-Columbian Collection, Washington, DC.