The Transitional No Crown Guard Weems

Longines first developed the 18.69 pocket watch calibre in 1895, and like their other movements at this time, by 1908 it was re-engineered as a thinner (7.75mm), slightly wider (39.75mm) calibre, becoming the 18.69N.

An incredible Weems delivered February 11,1938 featuring an extra transitional crown at four. The 6mm auxiliary crown on these first few pieces absent shoulder guards was almost instantly replaced with guards protecting it from being knocked or bumped. It heralded the replacement of the pin set 18.69N calibre with the introduction of the new 37.9 which allowed independent accurate use of the second-setting mechanism. The inner chapter ring remained 21mm and changed to 25mm in the months that followed.

The transitional no crown guard Weems highlights a rare insight in the evolutionary chapter of the one of history’s most famous pilot watches.

Turkish Touran dual time Longines pocket watch
An incredible and possibly unique Turkish survivor lying in the Longines museum. The Touran, with the name signed in the sub-second register had an 18.5mm turning chapter ring which was the size selected for the first two Weems. The modified 18.69N pin set dual time turning inner chapter movement bears the remarkable genetic code of the large 47mm Second-setting Weems models that followed 10 years later. Image courtesy – Vefa Borovali & Longines Museum.

The very first prototype Weems watch used an 18.69N pin-set pocket watch movement that was originally destined for the Turkish market in a Duble tour D’Heure (dual time) turning inner disc pocket watch retailed by the Turkish agent Nacib Djezvedjian. 

Rare ad featuring an elusive 37.9 Weems with crown guards and a 21mm chapter ring.

Whilst the very first Longines Weems Second-setting watch was not delivered till 30 November 1928, Longines archive records clearly note the repurposing of Turkish 18.69N pocket watch movements made more than a decade earlier for these first prototype pieces. 

This included Weems actual watch (serial # 3585867), that now rests in the Smithsonian, and piece #2 (3585868).

Two Turkish dual time pocket watch models used modified pin set 18.69N pocket watch movements with extra gear wheels.

The first with an inner dial had two timezones with two sets of hands and the second pocket watch, signed Touran, also featured an 18.5mm turning inner chapter that mirrored the exact size of the turning disc of the prototype Weems pieces.

Both are essential formative pieces in the Longines 47mm Weems history and lie in the Longines Museum. 

Whilst the large onion crown of the Weems and Lindbergh models enabled easy use with gloves, the pin set second-setting feature would be a challenge setting with gloves. Both of these pilot watches used robust pocket watch calibres for their entire production life.

longines-weems-_-lindbergh-move-37.9N
In this Longines movement schematic, both the 21 and 25mm inner discs are featured for the 37.9. The transitional auxiliary crown Weems was first delivered Feb 1938 with only a 21mm chapter. Two changes followed – a larger 25mm chapter and the addition of shoulders protecting the auxiliary crown in the next order a few months later.

The pin-set 18.69N calibre was used up until the robust 37.9 replacement order of February, 1938, in the Weems model.  The latter caliber, first developed in 1932 was 18 lignes and would be replaced by the 37.9N execution of 1941-2. Old stocks of the 18.69N continued to be used in the Hour-angle model into the early 1940’s.

With the dial out, the crown and the gear mechanism for turning the inner chapter enabling the second setting adjustment are clearly visible from the underside of the dial. The 37.9 calibre improved the pin setting adjustment used on Weems models up until February 1938.

A second transitional 6mm crown at four was added to the second generation of the Weems model allowing easier, faster independent rotation of the inner second setting chapter. This was a transitional experimental crown and the first known order existed without any shoulder or guard protection.

The pin setting adjustment common on pocket watches featured on Weems models up until 1938 when the model used the 18.69N calibre. The two functions of the time and adjustment of the inner second setting chapter were selected by pressing the pin set at four.

Much like the Omega and Rolex sports models that followed 20 years later, an improved version with shoulder guards protecting this second auxillary Weems crown was introduced within months.

All silver cased Weems sidereal time watch featuring the 37.9 calibre, a protected auxiliary crown and a larger 25mm inner chapter ring delivered July 1938.

The number of known surviving examples with this transitional crown can be counted on a hand. One of these examples exists in the Longines Museum with an unusual reference number 4214 marked.  To date it appears to be one of the only known pieces bearing this reference.

Admiral Byrds Weems watch movement
The magical nickel silver finish calibre 18.69N pin set pocket watch movement first created in 1908 was used by Longines for ten years of the Weems production and a similar length of time for the Hour-angle models. The Weems changed to the 37.9 calibre in February 1938 and the Lindbergh continued using the pin-set 18.69N for another 3 years. The transitional auxillary guard free crown was only seen on the Weems model.

Two other examples, both reference 5350 with this special transitional guard free crown were part of the very same order delivered to Wittnauer on 11 February, 1938 making them among the first known examples using the new 37.9 calibre.  One was regulated for civil time and the other sidereal and this order appears to be the earliest known of the new 37.9 calibre.  

Rare survivors – a very unusual pair of transitional auxiliary crown large Weems models. Both pieces without guard protection and delivered on the very same day in February 1938. One regulated for civil and the other sidereal time.

For the handful of known pieces, the movement was upgraded replacing the pin set pocket watch 18.69N, however the inner chapter ring remained 21mm.  The next known Weems order in July 1938 saw adoption of a protected crown and the use of a larger 25mm chapter ring.  Longines movement schematics point to both chapter ring sizes being used with the 37.9. 

A transitional Weems auxiliary crown model with the top off delivered to Wittnauer in February 1938. On can clearly see the movement marked Longines and Wittnauer.

Similarly, a Longines advertisement with an unknown publication date pictures a 37.9 guarded crown model with a 21mm chapter at this changeover juncture. To date, discovery of such an example remains elusive. Seemingly the transition to the new 37.9 movement, larger (25mm) more legible chapter ring and the new guarded crown happened simultaneously and almost immediately.   

A standard looking Longines advertisement with a highly elusive model. A Weems model using the 37.9 calibre featuring guard protection of the auxiliary crown and the small 21mm inner chapter ring. The model was almost immediately replaced by a larger 25mm chapter ring.

The production models of the 18.69N all came with 21mm inner chapter rings.  The introduction of the 37.9 calibre, was witness to an unguarded crown and use of the 21mm chapter ring. First introduced in February 1938, the next known order of July 1938 saw both a crown guard and 25mm chapter ring.  

Only the Weems model featured the experimental crown setup. The so called Hour-angle or Lindbergh used up stocks of the 18.69N caliber and transitioned directly to a 37.9 calibre with a protected guard version in 1942.

The Lindbergh model used the 18.69N until 1941 and transitioned directly to a protected auxiliary guard on the model. A few rare examples of the last generation of Hour-angle are found with all silver cases and essentially were using up parts and most pieces came in steel cases.

The evolutionary processes at play in the history of the large 47mm Weems development essentially stem from ongoing improvements to functionality of this pilot’s timepiece.  Robust, reliable pocket watch calibres and Grand feu oversized Arabic numeral enamel dials were the central to the watch.

A rare pair of Weems transitional crown models both delivered to Wittnauer in the same order of February 1938.

Incorporating an auxillary crown, crown guard protection and increasing the chapter ring size led to improvements in the second-setting capabilities piece of this functional tool watch.

The introduction of the 37.9 calibre replaced the pin set function with an extra crown allowing easier use of the second-setting function. 

The need to protect the crown from being knocked or bumped during flight was instantly recognized by the Longines technical team and pilot feedback giving rise to protective shoulders on both sides of the crown. 

A crown guard protecting this auxillary crown was developed within months of its predecessor’s arrival. 

The few surviving transitional crown pieces are an important reminder of the adaptive AND purposeful transformation of history’s most famous pilot watch.

The last series of Weems model using a steel case and the 37.9N, has the auxiliary crown with shoulders guarding it from accidentally getting knocked or bumped.

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