Here we a 1940 Ebel 6B/159 Air inistry WW2 RAF issue Pilot watch. It has the 30mm case with the Duralim centre and steel snap on bezel and case back. The dial has the aged tone to cream, with the black Arabic numerals and minutes/seconds track. It has wear to the left hand side, clear signs of its wear and use. The thermally blued hands are all original, with the bright tone. To the right is the well sized crown with coin edge for ease of winding. To the rear, the case back is signed with the Air Ministry ‘AM’ initials with the 6B/159 engraving below. It is marked with the serial number 14813. 
It is a Dennison case, as marked to the inside of the back. It has the reference 12322 with the case serial 4235, which matches the number to the front case section. 
The watch is powered by the Ebel calibre 99 movement, which has been recently serviced and is keeping reliable time.
 
The history:
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/159s were manufactured by Ebel, Omega, Jaeger-LeCoultre, Longines, Movado, Waltham, Cyma and Smiths. 
 
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.
 
Ebel 6B/159
The Ebel is considered one of the rarer 6B watches issued to pilots and navigators during WW2. 
 
Very few examples of the Ebel 6b/159 survived the rebranding to 6B/234’s. This means most had the markings crossed out and replaced with 234 for their new issue. Luckily this example maintains its original 6B/159 marking.
 
This example has a Dennison case which is marked with the reference 12322 with the serial 4235.
 
It dates to 1940 according to the design and serial number. There were two distinct batches in this period. One has the Goldsmith & Silversmiths Co Ltd marked case back, while the others didn’t. The earlier 1940 examples seemed more rushed, with variations in handsets.
 
Normally the year is after the serial number, but on this example, it is missing. The reason for this is not known. Production was rapid and watches were necessary on wrists, meaning the intricacies of date stamps etc were less important. This is the only example we have seen with the year code lacking.
 
The dial is clear and classic. It has the large railroad minute/second track around the exterior with the bold Arabic numeral hour markers. The dial was a silver tone but is prone to ageing closer to a cream tone. Our example has speckled black spots with wear on the left-hand side of the dial between 12 and 4 o’clock. Some may not like such a distressed dial, but we choose to leave the dial with these scars. They represent clear signs of use on a watch that was a vital companion in the skies for pilots. 
The hands are of the neat and elegant thermally blued spade and whip style. The tone has oxidised to a bright purple which catches the eye. The thin central second is also original. 
 
The case is petite measuring just over 30mm x 30mm. It has a lug to lug length of 27mm with a depth of just over 10mm. The case is formed of ‘duralim’ to the centre, which was a metal alloy. It is prone to darkening, pitting and corrosion. The bezel was formed of stainless steel, as was the caseback. 
The bezel has the flat polished surround holding the crystal, with the dished outer section. The sides of the case are flat, with the lugs being of a traditional elongated, tapered design. It has the fixed bar lugs which are good and sturdy. To the right of the case is the crown, which is a replacement. The case back snaps on tightly and has the clear issue engraving ‘AM 6B/159, 14813’. It has the polished finish with light marking from poor opening attempts. 
The inside of the case back is marked as ‘Dennison’ with the reference 12322. It has the serial number 4235. This serial matches with that of the front of the case. 
 
Inside is an Ebel calibre 99 manual wind movement. It has the jewel count of 15, with the sweep central second. It has been recently serviced and is keeping time to within 20 seconds variation per day. 
 
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 has signs of ageing. The original silver tone has darkened all over. There are black speckled dots and there is wear to the signing between 12 and 4 o’clock.
 
Hands:
The hands are all original. They are thermally blued and have oxidised with some purple/brown tones. There is no bending or scratching and they are in good condition. 
 
Glass:
The acrylic crystal is a replacement which is in perfect condition.
 
Crown:
The crown is formed of Stainless Steel and is a replacement, which is in good condition.
 
Case:
The case is formed of Duralite to the centre and shows signs of its age. There is scratching and darkening as expected with age. The bezel is stainless steel and has a polished finish, with some light scratching. The lugs are good, with the fixed bars being strong. 
 
Caseback:
The snap-on case back is stainless steel and has the polished finish. The issue markings are good and clear. There are some scratches from poor opening attempts. 
 
Strap:
The watch comes on a new leather strap for fixed bar lugs, which is glued in place. It is in unworn condition. 
 
Movement:
The movement is a Ebel calibre 99. It is a manual wind movement, with sweep central second. It has a jewel count of 15 and a frequency of 18,000 BPH.
 
The movement has been recently serviced. It’s keeping time to within + 20 seconds a day, with an amplitude of 300 degrees and a beat error of 1.0m/s.
 
Case dimensions:
Case width: 30.15mm
Case width with crown: 31.75mm
Case length: 30.15mm
Case length lug to lug: 37.3mm
Case Depth: 10.3mm
Lug width: 16mm