On 14 October 1991 MIL-W-46374F was published. Both SandY and Marathon had been making various types of Field Watches for the General Purpose categories of the MIL-W-46374E spec (Types 1 through 5). They simply modified the inscriptions on the case back to read MIL-W-46374F. That's how similar the E and F specifications were for Types 1 through 5.
The big news from the F revision was the creation of the Type 6 Navigator watch. The new MIL-W-46374F-6 specification (which superseded Air Force PD-496B of 26 Feb 1985) led to the creation of the Stocker & Yale P650, P660 and the Marathon 211 Navigators watches (plastic case). The Type 6's are fundamentally better-quality, hacking, Quartz watches with rotating GMT-style bezels. On top of these basic requirements for Navigation, the Type 6 parts of the spec also noted some special requirements: resistance to high altitude (low pressure) damage (35,000 feet for minimum of 60 minutes); greater magnetic protection (125±1 gauss magnetic field [compared with 14.5 to 15.5 gauss protection for the Type 1 - 5 watches]); and protection from "salt fog" and from Human perspiration.
Luminescent green Tritium vials were specified for the hands and hour marks for all types in the initial spec.
But Amendment 2 published 10 June 1994 allowed for the use of a different, "orange or red" color vial at the 12 o'clock position. This is important and useful, because it provides a quick way to gauge the date of a watch from just examining the dial. If it has an orange vial at 12 o'clock, it is likely a MIL-W-46374F watch assembled after June of 1994.
The case back markings on the MIL-W-46374F watches followed the specified 11 line pattern shown below. In the info page for the W46374B revision, we described what several of these inscriptions mean in detail. As with previous specs the Type 1 watches use the date of acceptance by the DoD. All other types use date of manufacture, if the date is required. Serial numbers are required only on the Type 1 watches. It seems that date and serial number requirements were not strictly enforced by the DoD from the "E" revision on. Few issue watches from that era have these "required" markings.
Caseback Markings US-Issue MIL-W-46374F Type 3 SandY 590
Value and Variety
A wide spectrum of watches have been made under the MIL-W-46374F specification. I have seen documentation for ten different models from SandY and Marathon made under the MIL-W-46374F specification. (from SandY, the P650, P660, P550Q, P550M, 590 and 490; and from Marathon, the 211, 359, 350A, and 348A). Two of those models, however, may never have been seen - the SandY P550Q (Quartz) and the SandY P550M (Mechanical) . If these watches were, in fact, ever purchased by the goverment, they would be among the rarest of the rare. They appear on several DoD QPL's (Qualified Products List), but they do not appear to ever have been ordered. This is one case where I would love to be wrong - as long as it means that I would get a SandY P550M for admitting my error.
SandY 490's and Marathon Type 1 mechanical watches are highly prized and sell for around $100, but the kings of the MIL-W-46374F spec are the Type 6 watches. The SandY P650 and the Marathon Model 211 Navigators (Plastic version) are among the most desirable Mil watches being collected and worn. I would guess that every Mil Watch collector has at least one Type 6 in his or her collection, or they are scheming to add one as soon as possible.
SandY P650's command over $300 used and New in Box examples have sold recently for over $500. The SandY P660, a stainless steel version of the 650 often sells for $400 used and can command $600 in NIB condition. The Marathon Model 211 plastic version of the Navigator sells for much less - typically between $125 and $150 in NIB condition.
Several people have asked if the so-called Marathon Stainless Steel (a Navigator watch similar to the Marathon 211 Navigator) is a MIL-W-46374F Type 6 issue. My best guess is no. I think that the Marathon SS was made under the Air Force specification PD-496B - which was superseded by the Type 6 portion of MIL-W-46374F in October of 1991. Most of the original Marathon SS's were made before then and could not have been made under the F revision.
Final Thoughts on this Popular Specification:
Its difficult to come up with exact figures, but I estimate that more than 2 million watches have been ordered using the MIL-W-46374 specification and its various amendments and revisions. More than 22 identifiable models from at least five different watch manufacturers have been made under these specifications from 1965 through the present time. It was, and is, one of the most frequently cited specifications in the world of military watches.