September 21, 1964: Deke Slayton, fellow Mercury astronaut and director of flight crew operations for NASA, drafts a memorandum to the Procurement and Contracts Division of NASA, stating the need for a standard flight crew wrist chronograph for all NASA astronauts:

A requirement exists for a highly durable and accurate chronograph to be used by Gemini and Apollo flight crews as an essential adjunct, or as a backup for spacecraft timing devices and for accomplishing time critical operations and experimental tests. In order to select a chronograph which best meets our overall requirements, it is necessary to accomplish a comparative evaluation of the better quality "off the shelf" chronographs under realistic operational conditions. The evaluation will take place during such flight crew training programs as the Gemini Mission Simulators, during spacecraft and other flight equipment testing in the altitude chambers, egress and recovery exercises, planetarium reviews, and during the first two manned Gemini flights. The evaluation will be of the basic "off the shelf" items; however, an analysis will also be made of any additional features and/or modifications that may be required.

It is highly desirable that we commence with this evaluation at an early date so that a standard flight crew chronograph can be obtained prior to the longer duration Gemini flights and the Apollo flights. The evaluation items should be available during the preflight training for the first two manned Gemini flight crews, which are now in progress. On this basis, quotations from various chronograph manufacturers meeting the specifications as listed in analogue 1, Statement of Specifications, should be reviewed by this organization by October 21, 1964. Immediately subsequent to this date, it is our intent to purchase locally at least one of each brand that meets, or very nearly meets, these specifications. Off the shelf chronographs which very nearly meet the specifications may be considered if they, in other regards, surpass the overall specifications. The manufacturer in this case may choose to reply to the request for quotations, however, NASA-MSC will make the determination as to whether or not the chronograph will be subsequently evaluated. It is estimated that a total of twelve chronographs are required for evaluation purposes.

/s/ Donald E. Slayton

The memorandum contains a "Suggested List of Manufacturers", which includes to the top watch makers of the day:

Elgin
Benrus
Hamilton
Mido
Lucien Piccard
OMEGA
Bulova
Rolex
Longines
Gruen

Slayton's memorandum also contains a "Statement of Specifications", consisting of the following:

STATEMENT OF SPECIFICATIONS

1. Accuracy - Must not gain or lose more than 5 seconds over a 24 hour period. Desirable to have an accuracy equal to or better than 2 seconds per 24 hours.

2. Pressure Integrity - The chronometer [sic] must be immune to large variances in pressure to include a range from 50 feet of water positive pressure to a negative pressure of 10 millimeters of mercury.

3. Readability - All disks, bands, and figures must be readable in various lighting conditions. The chronograph must be readable under both "red" and "white" lighting conditions to or beyond a 5 foot candle illumination intensity. Either a black face with white figures and numerals or black on white is satisfactory. The chronograph should not cause glare at the high illumination levels. A stainless steel case with a satin finish is preferred.

4. The chronograph must have stop-start elapsed dials with

a. Seconds to 1 minute
b. Minutes to 30 minutes
c. Hours to 12 hours or greater.

5. The chronograph must be shockproof, waterproof, and antimagnetic. In addition, the face cover must be shatterproof.

6. The chronograph may be powered electrically, manually or the self-winding type; however, it must be capable of being manually wound and re-set.

7. Reliability - the Manufacturer must guarantee the watch to operate properly under normal conditions for at least one year time period. Performance data and specifications should be supplied by the manufacturer. Manufacturer guarantee and/or warranty should also be included.

The same memorandum outlines the testing criteria for this official wrist chronograph. To be "flight-qualified by NASA for all manned space missions", a wrist chronograph must pass all of the following tests numerous times without failure of any kind:

1. High Temperature - 48 hours at a temperature of 160° F (71° C) followed by 30 minutes at 200° F (93° C). For the high temperature tests, atmospheric pressure shall be 5.5 psi (0.35 atm) and the relative humidity shall not exceed 15%.

2. Low Temperature - Four hours at a temperature of 0° F (-18° C).

3. Temperature Pressure Chamber - pressure maximum of 1.47 x 10exp-5 psi (10exp-6 atm) with temperature raised to 160° F (71° C). The temperature shall then be lowered to 0° F (-18° C) in 45 minutes and raised again to 160° F in 45 minutes. Fifteen more such cycles shall be completed.

4. Relative Humidity - A total time of 240 hours at temperatures varying between 68° F and 160° F (20° C and 71° C, respectively) in a relative humidity of at least 95%. The steam used shall have a pH value between 6.5 and 7.5.

5. Pure Oxygen Atmosphere - The test item shall be placed in an atmosphere of 100% oxygen at a pressure of 5.5 psi (0.35atm) for 48 hours. Performance outside of specification tolerance, visible burning, creation of toxic gases, obnoxious odors, or deterioration of seals or lubricants shall constitute a failure. The ambient temperature shall be maintained at 160° F (71° C).

6. Shock - Six shocks of 40g's each, in six different directions, with each shock lasting 11 milliseconds.

7. Acceleration - The test item shall be accelerated linearly from 1g to 7.25g within 333 seconds, along an axis parallel to the longitudinal spacecraft axis.

8. Decompression - 90 minutes in a vacuum of 1.47 x 10E-5 psi (10 E-6 atm) at a temperature of 160° F (71° C), and 30 minutes at a 200° F (93° C).

9. High Pressure - The test item shall be subjected to a pressure of 23.5 psi (1.6 atm) for a minimum period of one hour.

10. Vibration - Three cycles of 30 minutes (lateral, horizontal, vertical, the frequency varying from 5 to 2000 cps and back to 5 cps in 15 minutes. Average acceleration per impulse must be at least 8.8g.

11. Acoustic Noise - 130dB over a frequency range from 40 to 10000 HZ, duration 30 minutes.

NASA performs the tests several times on the various wrist chronographs it previously obtained. Only the OMEGA Speedmaster passes NASA's rigorous testing. All of the other watches fail NASA's tests.

March 1, 1965 - NASA, in a memorandum drafted on this date, outlines the results of its tests on the various wrist chronographs:

Environmental tests and test results for the chronographs are outlined in the attachment to this memorandum. The following major discrepancies were found during environmental testing:

a) Rolex - It stopped running on two occasions during the Relative Humidity Test and subsequently failed during High Temperature Test No. 1 when the sweep second hand warped and was binding against the other hands on the dial. No further tests were run with the Rolex chronographs.

b) Longines Wittnauer - The crystal warped and disengaged during the High Temperature Test. The same discrepancy occurred on a second Longines Wittnauer during Decompression Test No. 8. No further tests were run with Longines Wittnauer chronographs.

c) Omega - It gained 21 minutes during the Decompression Test and lost 15 minutes during the Acceleration Test. The luminescence on the dial was destroyed during testing. At the conclusion of all testing the Omega chronograph operated satisfactorily.

The results of operational evaluations by the astronauts show a unanimous preference for the Omega chronograph over the other two brands because of better accuracy, reliability, readability and ease of operation.

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They gave them a watch, and probably said heck lets use Count-Down name on next model :-)