Surviving Photographs of Self Winding Clock Co./Western Union “Naval Observatory Time” Clocks: An Illustrated Catalogue

A working catalogue compiled from public photographic archives.

Educational edition - a non-commercial research resource. Revised 19 September 2026.

The Self Winding Clock Company of New York (1886–c. 1969) manufactured battery-wound clocks that were corrected once an hour by an electrical pulse carried over Western Union’s telegraph lines and referred to the master clock of the U.S. Naval Observatory; their dials read “Naval Observatory Time/Western Union.” Although more than 150,000 were in service by 1930, the firm is sparsely documented online. This catalogue assembles photographs in which such a clock is identifiable.

Contents

1. Scope and method

Entries were located in freely accessible digital collections and verified by inspection of the image itself. Two grades of identification are used. Dial confirmed denotes a photograph in which the “Naval Observatory Time/Western Union” wording, or the Self Winding Clock Co. imprint, is legible. In situ denotes a clock visible on the wall of a documented Western Union workplace where the make cannot be read directly; because Western Union offices were equipped from this system, such clocks are very likely of the same manufacture, but the attribution is not certified here.

2. Clocks with a legible Western Union/Naval Observatory dial

Union Pacific depot clock, Union Station depot relay office, Colorado, clock c. 1940; photograph recent
Fig. 1. The full dial reads "NAVAL OBSERVATORY TIME/WESTERN UNION" with the red lightning bolt, and "SELF WINDING CLOCK CO. INC. NEW YORK" at the foot. [dial confirmed]
Union Station depot relay office, Colorado, clock c. 1940; photograph recent. Source: Broomfield History Collections, acc. 1979.14.1 (via DPLA). Per the accession record, trainmen set their watches by it; it was "tied into Western Union circuits, set twice a day to Naval Observatory time, as were all clocks on system." The digital photograph is recent; reproduced here at reduced size for documentation.
The Daily Ardmoreite office clock, Ardmore, Oklahoma, mid-20th century
Fig. 2. The same square-cased dial - "NAVAL OBSERVATORY TIME/WESTERN UNION" - held by two members of the newspaper staff. [dial confirmed]
Ardmore, Oklahoma, mid-20th century. Source: Ardmore Public Library/Gateway to Oklahoma History (Oklahoma Historical Society). Captioned "Old Western Union clock that hung in the Daily Ardmoreite office for many years. At right is Suzanne McLain of the Ardmoreite." The repository grants research, teaching, and private study; shown here for that purpose.
WSB radio studio, Atlanta Biltmore Hotel, Georgia, 1920s (recorded 1920–1929)
Fig. 3. A wall clock mounted high on the studio wall, seen through the observation glass; the tablet above the dial reads "NAVAL OBSERVATORY TIME/WESTERN UNION." [dial confirmed]
Atlanta Biltmore Hotel, Georgia, 1920s (recorded 1920–1929). Source: Georgia State University Library, Special Collections/Digital Library of Georgia. Radio stations were characteristic subscribers, requiring exact time for broadcast. Georgia State University marks it in copyright with educational use permitted (InC-EDU); it is plausibly public domain by age (1920s) as well.
Street clock, downtown Atlanta, Atlanta, Georgia, 1951
Fig. 4. A public sidewalk clock, its dial reading "Naval Observatory Time/Western Union" and imprinted "Self Winding Clock Co., New York," with a passer-by looking up at it. [dial confirmed]
Atlanta, Georgia, 1951. Source: Atlanta Journal-Constitution, June 17, 1951 (via Newspapers.com). From a newspaper photo feature on the city's public clocks.

3. Clocks in situ in Western Union workplaces

Operating room, Ellicott Square Building, Buffalo, New York, about 1896
Fig. 5. A round wall clock mounted high at top-centre, above a floor of operators at typewriters and telegraph instruments. [in situ]
Buffalo, New York, about 1896. Source: Smithsonian, Archives Center, NMAH - Western Union Telegraph Company Records (NMAH.AC.0205). Among the earliest examples in the catalogue (rotary-movement era).
Operating room, Phoenix Building, ninth floor, Chicago, Illinois, 1901
Fig. 6. Round wall clocks - one mid-left by the windows, another on the far-right wall - over a large hall of operators, with a visitors' gallery above. [in situ]
Chicago, Illinois, 1901. Source: Smithsonian, Archives Center, NMAH - Western Union Telegraph Company Records (NMAH.AC.0205). Illustrates the scale that Western Union time distribution reached.
Operating room with a roller-skate messenger, Western Union operating room, United States, ca. 1936
Fig. 7. Three round wall clocks (the largest a double-faced bracket clock on the pillar); women operators, overhead routing signs, and a messenger on roller skates. [in situ]
Western Union operating room, United States, ca. 1936. Source: Baker Library, Harvard Business School - "Women Working, 1800–1930". The most populated single frame in the set. Harvard dates it ca. 1936 (after the 1930 public-domain cutoff); reproduced here at reduced size under fair use for scholarship.
Western Union Telegraph & Cable office, Oklahoma, c. 1910s
Fig. 8. A tall wooden regulator on the left wall; staff at the key table; a "WESTERN UNION/MONEY/TELEGRAPH & CABLE" placard on the desk. [in situ]
Oklahoma, c. 1910s. Source: Oklahoma Historical Society/Gateway to Oklahoma History. The dial maker's name is not legible; recorded as an in-situ office clock of unconfirmed brand. The repository grants research, teaching, and private study.
Western Union branch office, Ardmore, Oklahoma, c. 1920s
Fig. 9. A wall clock hung centre-back; operators at the tables, and a "Western Union Standard Time" service board at right. [in situ]
Ardmore, Oklahoma, c. 1920s. Source: Ardmore Public Library/Gateway to Oklahoma History. Same town as the Ardmoreite clock; a full working-office view. The repository grants research, teaching, and private study.

4. The source of the signal

Naval Observatory transmitting clocks, U.S. Naval Observatory, Washington, D.C., 6 January 1916
Fig. 10. The two Self Winding Clock Co. master (transmitting) clocks, with the chronograph drum and the switchboard that keyed the time signal onto Western Union's wires. [the source]
U.S. Naval Observatory, Washington, D.C., 6 January 1916. Source: U.S. Naval Observatory Time Service (via Internet Archive). Originally catalogued as "Plate 217." The source end of every example above. A work of the U.S. federal government.

5. How the national time network worked

The clocks in this catalogue were the visible end of a chain that reached from an astronomer’s telescope to a wall in a country depot. At the U.S. Naval Observatory in Washington, true time was determined from the stars and held by three precision pendulum clocks - the reference standard, not the Self Winding Clock Co. product - sealed in an underground vault.

A Naval Observatory master standard clock in its glass case, 1930
Fig. 11. One of the three Naval Observatory master standard clocks (a Riefler-type regulator) in its glass, partly-evacuated case - the reference the Self Winding Clock Co. transmitting clocks were checked against; not itself an SWCC clock. Source: George W. Gray, “How the Nation Keeps Time,” World’s Work, 1930 (public domain).

Each day at 11:50 a.m. Eastern, Western Union handed its wires to the government. A “sending” clock, checked against the vault standards to a fraction of a second, was looped through transcontinental lines to San Diego, Key West, Arlington and Annapolis; at the stroke of 11:55 it “threw a single switch: ‘Click!’ and standard time was going out to all the world.” The noon signal ran five minutes, with a ten-second silence just before the stroke of noon, and was sent three times a day - noon, 10 p.m. and 3 a.m. Eastern (World’s Work, 1930).

Locally, a Western Union office kept a master clock, set right at noon by that signal, which then corrected every subscriber clock in the town once an hour - which is why the dials read “Naval Observatory Time, hourly by Western Union.” By 1930 the article counted “more than 150,000 subscribers.” A business paid roughly $15 to $30 a year, “including installation, complete maintenance, and the time service” (Milham, Time and Timekeepers, 1923).

6. How the clocks were installed and wired

A self-winding clock needed no power cord: two dry cells inside the case drove a small motor that rewound the mainspring once an hour. The only outside connection was a thin, low-voltage synchronizing wire that entered the back of the case and ran into the wall, with the case mounted flush - which is why these clocks look wireless in nearly every photograph.

Self Winding Clock Co. installation wiring diagram, Sheet B-2
Fig. 12. The company’s installation sheet: the batteries sit inside the case (the two boxes), the blue and green leads are internal, and a single synchronizing wire enters at the top and runs into the wall behind the flush-mounted case. Source: Self Winding Clock Co. service manual, Model “F,” c. 1945 (Internet Archive).

A whole building was run as a system: one master clock, usually in a back room, drove the subscriber and “secondary” dials - and program circuits that rang bells on a schedule - over low-voltage wiring threaded from room to room. The public saw a wall of clocks that looked wireless; the wiring converged out of sight at the master.

7. A note: the clock that timed an execution

A measure of how completely these clocks stood for “the correct time”: at the execution of Bruno Hauptmann (the Lindbergh case) at the New Jersey State Prison in April 1936, the death chamber’s official clock was a Western Union/Naval Observatory Time clock. The Brooklyn Daily Eagle’s account records the officials checking it in the moment - “It is 8:35. There is argument about the time - is the clock two minutes fast?” - the dial reading, as always, “Naval Observatory Time, hourly by Western Union.”