Recently, a close inspection of two bolts removed from the ship in the 1992-1996 restoration revealed that the bolts were stamped “YS MINE CO.” Subsequent research showed that the stamp belonged to the Parys Mine Company of Greenfield Valley, Holywell, North Wales, (the “PAR” of the name “Parys” was missing from the stamp). This company had supplied at least some of Constitution’s copper bolts for her keel structure in the 1790s.

Naval Heritage and History Command Detachment Boston Collection.
A 1795 Parys Mine Co. marked bolt (bolt no. C82) removed from Constitution‘s keel during the 1992-1996 restoration. The bolt number is a unique identifier assigned by NHHC Detachment Boston. [Naval Heritage & History Command Detachment Boston Collection]
Both bolts are 1 3/8 inch in diameter. One of the bolts (identified at bolt no. C82 by NHHC Detachment Boston, pictured above) today measures 56 1/2 inches long, or a little over 4 1/2 feet in length. Originally, it could have been more than 10 feet in length. It was removed from the keel structure about a third of the way aft between the fore and main masts.

An architectural drawing of USS Constitution's after keel section from the 1992-1996 restoration. [Courtesy Naval History & Heritage Command Detachment Boston]
An architectural drawing of USS Constitution’s after keel section from the 1992-1996 restoration. The vertical objects represent copper bolts driven through the keel structure. [Courtesy Naval History & Heritage Command Detachment Boston]
We know that Constitution’s keelsons were replaced in the extensive 1927-31 restoration, though it appears that the original copper bolts were able to be saved and reused during the process. According to a 1931 “Research Memorandum” written by Lieutenant John Lord, Superintendent of Restoration, the bolts were “backed out,” that is, pounded back through their holes, so that the old, rotted sections of keelson could be removed. Lord noted:

“The old laminated keelson, consisting of short sections of live oak, was found to be in a badly decayed and weakened condition and broken in two parts abaft the foremast step. The old keelson was entirely removed. The copper through bolts, 1-3/8 inch diameter, were partly sawed off and backed out through the floor timbers and keel.”1

Once that was accomplished, the new lower and upper keelsons were installed, new fastener holes were drilled to match up with original holes on the keel and floor timbers, and then the original 1795 copper bolts were pounded back into the keel structure. This process is confirmed once again in Lord’s memorandum:

“The upper and lower tiers of keelson timbers were bored from the outside, following the old holes bored through the keel and floor timbers. The keelson timber through-bolts were 8’4” long, and only about five feet existed between the bottom of the dock and the underside of the keel for boring purposes. The problem was solved by the use of knuckle joints attached to the auger rod.”2

[Courtesy Naval History & Heritage Command Detachment Boston]
USS Constitution Midship Section Plan No. 34535, January 1926. The plan indicates the 1 3/8 inch copper bolts that would hold the new keelsons to the floor timbers and keel. [Courtesy Naval History & Heritage Command Detachment Boston]
Lord confirmed that copper was reused in the ship: “Many of the articles and materials have been used over again…Some old copper fastenings and a small amount of iron fastenings [were removed,] straightened and used again.”3  He was careful to preserve as much original material as possible during the extensive 1927-1931 restoration. Lord explained the result of these efforts in his final report:

“During the process of restoration extreme care has been used to preserve much of the old material as could be used in the rebuilding and as a result approximately fifteen percent of the old material remains in the ship.  Of this about ten percent is estimated to be material which was built into the ship originally.”4

Sixty-five years later, in the 1992-1996 restoration, NHHC Detachment Boston used non-destructive testing and recording methods to document the condition of wood and copper fasteners in the oldest part of the ship. Constitution’s keel was x-rayed to determine if the copper bolts therein were in sound condition, partially sound condition, or very poor condition. The bolts in sound condition were left undisturbed, those in partially sound condition were reinforced with support from another bolt bored nearby, and the bolts in poor condition pulled and replaced. The x-rays saved time and effort and allowed the Detachment to leave more “original” material undisturbed in the ship’s keel structure.

A positive print of an x-ray showing at least three copper bolts, including bolt no. C82, on Constitution's keel. The bolts are the darkened vertical lines in the center of the x-ray. [Courtesy Naval History & Heritage Command Detachment Boston]
A positive print of an x-ray showing at least three copper bolts, including bolt no. C82, on Constitution’s keel. The bolts are the darkened vertical lines in the center of the x-ray. [Courtesy Naval History & Heritage Command Detachment Boston]

Until very recently, the story of “Old Ironsides'” copper bolts focused on Paul Revere with the mistaken belief that he had manufactured all of the ship’s copper fasteners. To test this theory, during the 1992-1996 restoration, NHHC Detachment Boston and MIT’s Center for Materials Research in Archaeology and Ethnology (CMRAE) established a proposal to “define a metallurgical signature with which to identify copper fasteners used on historic ships.”5 “Historic ships” is mentioned because the CMRAE study did include copper bolts from USS Constellation, HMS Victory and HMS Trincomalee. Based on the location of several bolts removed from Constitution‘s keel structure (including the two Parys Mine Company bolts) the Detachment Boston and CMRAE assumed those bolts were original and therefore had to have been manufactured by Revere.

According to scientists at CMRAE in 1993, “The technical examination [would] include [a] determination of the metal or alloys from which the pins [were] made…”CMRAE’s premise hinged on the notion that copper bolts removed from Constitution could be “dated securely” and would exhibit distinct metallurgic characteristics. Several dozen copper bolts of varying diameters were removed from different parts of the ship, including the “worm shoe” (or false keel) on the bottom of the keel, the keel/keelson/deadwood, the forward edge of the cutwater, the transom (v-shaped beams that cross the stern post), and the garboard strake (the lowest exterior hull plank next to the keel). The test results showed that all of the bolts were made from nearly pure copper with little to no unique composition. Unfortunately, this neither confirmed nor denied that the keel bolts were made by Revere. Of the three copper bolts that were presumed to have been made by Revere based upon their size and location in Constitution‘s keel, two, in fact, were from the Parys Mine Company in Wales. This was confirmed by the stamps that were overlooked in the 1990s testing and discovered nearly a quarter of a century later. Indeed, all the bolts tested were compositionally identical regardless of whether they were manufactured in Great Britain or America.

[Naval History & Heritage Command Detachment Boston Collection]
A Parys Mine Co. bolt cut lengthwise for testing at CMRAE. [Naval History & Heritage Command Detachment Boston Collection]
Lt. John Lord was very conscious of preserving as much “original” material in Constitution as possible. His final report delineated how much “original” material he believed was left in the ship:

“Old materials which were left in the ship include the outer keel, the lower futtocks or transverse frames, such as floor timbers, crotch timbers and some of the first futtocks, the lower part of the stem and apron, the lower section of the stern post, about thirty percent of the planking below the waterline, certain large oak stern knees, and other shaped pieces used to tie together the lower main structures of the ship; about 50 percent of the breast hooks; about 35 percent of the oak knees.”7

NHHC Detachment Boston shares in Lord’s goal and strives to preserve Constitution‘s “original” material. The Parys Mine Company revelation not only helps to increase our knowledge of Constitution‘s 1790s construction materials, but reminds us that, with each restoration, our understanding and interpretation of the ship continues to evolve. Who knows what discoveries are in store for the 2015-2017 restoration!

[Courtesy Naval History & Heritage Command Detachment Boston]
Constitution‘s 220-year-old original keel, photographed on February 1, 2016. This is the section from which the Parys Mine Company bolts were removed in 1992. The 1995 copper sheathing was removed in the fall of 2015 at the start of the current restoration. [Courtesy Naval History & Heritage Command Detachment Boston]

 – M. M. Desy and K. Monea


[1] [Lord, LT John A.] “U.S. Frigate CONSTITUTION (IX21) – Research Memorandum”, date stamped Nov. 27 1931, page 12.

[2] Ibid, 13.

[3] [Lord, John A.] “U.S.S. CONSTITUTION RESTORATION 1927-1930”, 49.

[4] Ibid.

[5] Patrick Otton, Technical Writer, Naval History & Heritage Command Detachment Boston, 7 May 1993, Memorandum.

[6] Director, CMRAE/MIT – 1 June 1993, Memorandum.

[7] [Lord, John A.] “U.S.S. CONSTITUTION RESTORATION 1927-1930”, 49.

The Author(s)

USS Constitution Museum