The 1815 Chronograph is 39.5 mm in diameter, and it is actually slightly thinner than the Patek 5170, at 10.8 mm. The movement is the Lange caliber L951.5, and it’s 30.6 mm in diameter, and 6.1mm thick. Here we have a very pleasantly slim, really refined hand-wound flyback chronograph movement with all the wonderful visual impact of the Datograph but with a bit less bulk. I am really not sure why A. Lange & Söhne is sometimes thought of as a maker of bulky watches – now, it’s true that some of their watches, especially high complications, can be rather thick affairs but they’re hardly alone in that.
Honestly, I think part of the problem is that a good-sounding narrative can sometimes obscure reality; the idea of “massively overbuilt German watchmaking” has stuck to A. Lange & Söhne like glue, but they make some very slim, elegantly simpleas well – the Saxonias are a perfect in point – and the 1815 as it turns out is actually slightly slimmer than the most technically comparable Patek. (A better comparison with the Datograph might be something like the Patek 5905P annual calendar chronograph, and as it turns out, that watch has a 33 mm movement that’s 7.68 mm thick, which is in the same ball park as the Dato’s movement, at 31 mm x 7.9 mm.)