Jaeger-LeCoultre Mark 11, caliber 488SBr

Certain watches seem to have a strong mystique, something which draws people to seek them out, research them and share their appreciation; the Jaeger-LeCoultre Mark 11 is just such a watch. Consider the circumstances:

--- Produced some 60 years ago, but only for five years, 1948-1953, and in a total of 2950 pieces

--- One of only two models (along with IWC) conforming to the British Ministry of Defense standards for navigators' watches, the original "pilots' watch"es, establishing the now-iconic design

--- 35mm diameter, with brushed, stainless steel screwback case and magnetic shielding

--- Powered by one of the most highly-regarded simple wristwatch movements ever, produced by the great movement manufacture JLC; a caliber only available in this model watch

This watch has a large potential audience: a handsome and original example of an illustrious and popular design, vintage, issued military, reliable and decently rugged and wearable today, historic individually and as a group, horologically significant and excellent...and exceptionally rare. As a bonus they are nearly impossible to fake because the movement was used in no other models, and is easy to recognize.

Many more expert than myself have researched and written about the JLC Mark 11; a couple of my favorites are Paul Shepard's fascinating and extraordinarily thorough Jaeger-LeCoultre Navigatorís Mark 11 Wristwatch Tracking Page and Greg Steer's excellent comments on RAAF Mark 11s. My own article on the Mark 11's predecessor, both as watch and movement, the JLC WWW may also be of interest.

The British Ministry of Defense specifications for the Mark 11 are referred to as 6B/346, and include these requirements:

-- incorporates a highly-accurate 12-ligne, 36-hour keyless Swiss lever movement with 16 jewels, Glucydur balance with Nivarox Breguet-type hairspring and non-magnetic curb pins

-- the case is to be stainless steel, waterproof to 20 feet and magnetically screened, with a screwed-in back and Perspex crystal

-- the movement must stop when the crown is pulled for time-setting

-- the soft iron dial is matte black with white Arabic numerals and minute track, and luminous cardinal markers and hands

The relevant page looks like this:

Even if one has never seen an orginal Mark 11, the look is likely instantly comfortable and familiar. The white speckling on the dial is the soft iron showing through black paint, indicating an original finish. Under a loupe these 'sparklies' really do look like stars against a black sky!

Click the pictures for even larger!

Screwed-in stainless steel back and anti-magnetic soft-iron inner cover. Engraved markings indicate: MOD reference, Royal Australian Air Force distribution, watch number 580 of 1953 issue year. Of the total 2950 JLC Mark11s, 1020 were used by the RAAF, with 600 of those from 1953, the last year of issue.

My watch has been fitted with a wonderful display back. While negating any anti-magnetic properties it does allow a spacious view of the beautiful and historic movement. The 16-jewel Cal. 488SBr is 12.5 lignes (about 28.5mm diameter) and 5mm thick, and as specified by the MOD and indicated by its nomenclature, pulling the crown stops the movement (S) and the hairspring has a Breguet terminal curve (Br). Its roots are in the 1930s, and while there are over a dozen variations of this ebauche, the 488 is one of the most highly developed. A brief survey of these notable JLC movements may be found in my article JLC's Classic Ebauche.

The brushed metal arch across the top of this picture holds a small wire loop which contacts the balance to stop the movement when the crown is pulled for setting. As shown, the polished bolt at right has pushed the hook-end upwards, and thus the opposite end down over the balance:

The business end of the stop-seconds mechanism, one side of the gorgeous sculptured and polished anchor and pallet jewel, properly striped and anglaged bridgework:

This is the cock which holds the center-seconds jewel, along with the spring which tensions the stem:

Lovely and functional brushed case and bezel, big crown perfect for winding:

Extraordinary wiew from the back!

Please check out the rest of my watch Articles and pics:

I hope you enjoyed this!

June 13, 2007

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