Here we have a good example of an all original 1940 Longines 6B/159 WW2 RAF Pilot watch. It has the rare full stainless-steel case, measuring 32.25mm with the snap-on bezel and case back. The dial is bright and nicely aged, with the black Arabic numerals and minutes/seconds track. It has a pleasing even speckled patination. The thermally blued hands are all original, with the standout Spade hour hand and Diamond tip minute hand. To the right is the original, well sized onion style crown. To the rear, the case back has the signing ‘AM 6B/159’ with the serial number 10232, which is a very low serial number. Inside it is signed with the reference 21250 and batch number 464. The watch is powered by the Longines calibre 12.68N movement, with matching 1940 serial number ‘6092590’. It has been recently serviced and is keeping reliable time.
 
The dreamer in you might allow you to imagine the watch on the wrist of a Battle of Britain Spitfire pilot and this might well have been the case. With the very early 1940 serial number, this watch will have been ready to be the vital tool on the wrist, to aid British pilots over the channel in the war defining battle.
 
The 6B/159 watches were issued to pilots and navigators in the RAF who required extremely accurate timekeeping. Other crews with less sensitive timekeeping needs were issued 6B/234 watches. The 6B’s were manufactured by Omega, Jaeger-LeCoultre and Longines, with the most famous being the Omega example. However, the Longines examples are rarer than the Omega 6B/159s and arguably more distinctive. The non-traditional diamond shape to the minute hand is eye-catching, as opposed to the Omegas ‘whip’. The crown is also standout with its larger size and onion design. 
 
The full Stainless Steel cased Longines are very rare. They were produced in the very earliest batches supplied in 1940. Most also lack the date numbers next to the serial number, such as this example. They are much more desirable due to the comparative rarity and durability of the case, compared to the Duralim centres.
 
The 6B code is the RAF stock code for navigational equipment to be used onboard an aircraft. The watches have the clear central second hand, vital for accurate timing and use in an aircraft. To further aid this, the central second hand also has hacking function, allowing for exact second hand setting.
 
The watches were vital in navigation and could be used to make dead reckoning calculations. Dead reckoning is the process of calculating the current position of a moving object (a plane), by using a previously determined position (fix) and incorporating estimates of speed, heading and elapsed time.
 
With increasing appreciation of these pieces and Longines drive to embrace heritage, at Baselworld in 2018, Longines announced the Longines Heritage Military RAF Re-Edition watch. This is a full steel construction, with a larger case size of 38.5mm. It is an excellent modern re-issue with the faux patina dial and handset. 
 
Why not get yourself an original Steel example? These are beautifully simplistic, yet reliable and sturdy timepieces, that have a story to tell.
 
Please see the images as these compliment and aid the description provided below.
A further condition report is below.
 
Dial: 
The dial is original and is in good condition for the age. It is an off-white tone with speckled patination associated with age. The signing is good and clear in the black tone, without wear. The minutes/seconds track and hour markers are good and clear. 
 
Hands: 
The hands are all original. They are thermally blued and have oxidised with some purple tones. There is no bending or scratching and they are in good, aged condition.  
 
Glass: 
The acrylic crystal is a replacement which is in very good condition.
 
Crown: 
The crown is formed of Stainless Steel and is original. It is in good condition and has the famous design. 
 
Case:
The case is formed of Stainless Steel and is in good condition for the age. It has the polished finish to the top, with light scratching. The sides have the lightly brushed finish. The bezel is stainless steel and has a polished finish, with some light scratching. The lugs are good, with the fixed bars being strong. The slots to pop the bezel and case back off have rough edges. The rear of the lugs have the stress fractures to the centre, common from the casting techniques used by Longines in this period. These do not affect the strength of the case.
 
Caseback:
The snap-on case back is stainless steel and has the polished finish. It has marking from being on a single piece strap in its life. The issue markings are clear and original.  
Strap: 
The watch comes on a period leather strap with metal tabs for fixed lugs. It is in good vintage condition. 
 
Movement: 
The movement is a Longines calibre 12.68N. It is a manual wind movement, with sweep central second. It has a jewel count of 16 and a frequency of 18,000 BPH. 
 
The movement has been recently serviced. It’s keeping time to within +/- 10 seconds a day, with an amplitude of 340 degrees and a beat error of 2.9m/s.
 
Case dimensions:
Case width: 32.5mm
Case width with crown: 35.25mm 
Case length: 32.5mm 
Case length lug to lug: 42.3mm
Case Depth: 11.5mm
Lug width: 16mm