IWC Big Pilot’s Heritage Watch 48 (Ref. 5103)

I am proud to introduce the first ever subject of my blog as the striking IWC BIG PILOT’S
HERITAGE WATCH 48. Few timepieces carry as much historical gravity as the B’Uhr, an
abbreviation for Beobachtungs Uhren, translating to Observation Watch in German. The
original B’Uhr was crafted to the most exacting and demanding standards of the time
period. IWC has reinterpreted the piece to embrace and exceed the most exacting
and demanding standards of today.

IWC has reinterpreted the piece to embrace and exceed the most exacting
and demanding standards of today.

From 1939 to 1945, the B’Uhr was produced by five manufactures, four of German origin and IWC of Switzerland. The timepiece was manufactured for the very specific function of aiding bombardiers during their missions, and the topology and design of the timepiece reflected that purpose clearly. It is interesting to note that the timepiece was not the property of the bombardier, but was provided for use during a respective mission and was returned to the appropriate command upon completion of the assignment.

IWC gave admirers of the B’Uhr an early holiday present this year by introducing two new B’Uhr inspired models. Reference 5104 (limited to 100 pieces), which at 55 mm and a movement providing 46 hours of power reserve, is a fitting homage to the original and will certainly be lust-worthy within the collector community. But as someone who likes to wear what he collects, the Big Pilot’s Heritage Watch 48 (limited to 1000 pieces), is certainly more befitting. The Heritage 48 transforms the essence of the B’Uhr into a modern timepiece with superlative performance, architecture, construction and wear-ability.

The Case

The case of the vintage B’Uhr was 55 mm, this was necessary to accommodate the large manual wind pocket watch movements of the time.  The size was also advantageous for the designated navigation process.  The Heritage 48 sports a more pragmatic 48 mm case, finely crafted from titanium. The weight of the 48 mm case is 122.5 grams.  This is relatively light  compared to my 46 mm Big Pilot (Reference 5009), which weighs in at 145 grams.

In the historical design, the case employed an inner iron core, protecting the mechanism from magnetic artifacts produced by aviation equipment.  The Heritage 48 follows suit but with an added case-back window, which allows viewing of the remaining power reserve of the movement (referenced in days).

A noticeably large crown adorns the Heritage 48, which is historically consistent and significant. An unusually large crown was necessary for the gloved operator to handle the crown with ease while in flight.  Unlike the Big Pilot, the crown of the Heritage 48 does not screw down into the case, allowing for direct and quick accessibility to the setting function.

The Strap

The long calfskin leather strap with pin buckle is sewn together at the ends of the two sections.  In a historical context, this design allowed the pilot to wear the timepiece on top of his flight jacket, and prevented a circumstance where the pin buckle could become detached,  resulting in loss of control of the timepiece.  In modern context, this supple strap sits surprisingly well on the wrist and the unique design provides a definite sense of security that the timepiece will stay exactly where intended, even during rigorous activity.

Dial and Hands

The focal point in the design of the dial and hands was undoubtedly the function of supreme legibility. The dial and hands of the Heritage 48 has very much in common with vintage B’Uhr. A triangle surrounded by two dots resides at 12 o’clock, which purpose is to serve as a point of orientation for the pilot, even in very poorly lit conditions. Like the original, the Heritage 48 utilizes blued metal hands filled with highly luminous material. While the original B’Uhr features a central sweep seconds hand, the Heritage 48 displays the seconds in a subsidiary dial located at 6 o’clock. Furthermore, a date window is elegantly integrated into the subsidiary seconds dial.

Movement

Among the five manufacturers, there were a number of movement used in the production of the vintage B’Uhr. IWC utilized vintage calibre 52T. Movements were expected to perform to exacting chronometer standards. Movements were also required to have a stop-seconds function (for accurate synchronization) and utilize a Breguet balance spring. IWC manufactured manual-wind calibre 59125, which powers the Heritage 48, offers vast improvements to performance as compared to the original B’Uhr.

This very well crafted and finely decorated movement supplies an extremely impressive 192 hour power reserve. Unlike many manual wind movements, which experience noticeable timing fluctuations related to the amount of power reserved in the mainspring, calibre 59125 offers unusually stable and accurate timekeeping throughout the entire 8-day period. This is made possible because this movement is actually capable of supplying 9 days of power, however after 8 days the balance is intentionally stopped, hence not allowing the movement to operate under less than an ideal torque environment.  In addition, a round window on the case back displays the number of days left before the timepiece requires re-winding.

Lastly, in consideration of the oversized crown and the potential consequences of the handling leverage, IWC has integrated a friction clutch to prevent over-winding of the manual wind movement. This is a particularly well thought out feature and will hopefully be more prevalent amongst other timepieces adorned with larger crowns.

Specs

I tested the Heritage 48 over an 8 day period. The piece was tested in 6 positions, allowing for a stabilization period between each position. X represents the average daily timing rate in seconds and the average amplitude in degrees. The performance of the movement was remarkably stable , even when the power reserve was near depletion. As discussed previously, this is partly due to a brake which stops the balance wheel after 8 days, even though enough power remains in the mainspring to operate the timepiece for another 24 hours, but at compromised performance. The accuracy of the power reserve length and display indicator were very consistent with the 192 hour manufacturer’s tolerance.

Day 1 +3.9 seconds per day

Day 2 +3.9 seconds per day

Day 3 +3.6 seconds per day

Day 4 +4.1 seconds per day

Day 5 +4.6 seconds per day

Day 6 +5.9 seconds per day

Day 7 +6.1 seconds per day

Day 8 +6.5 seconds per day

My Take

My take on this timepiece is rather simple… I really want one. It is a compelling timepiece on so many levels, including design, innovation, function, exclusivity, value and superior technical performance. Much like my Big Pilot Ref 5009, the timepiece feels absolutely fantastic on the wrist. I strongly encourage you to take one for a test drive before the limited edition of 1000 are all accounted for.

Until next time,

Art Bodin