If you think that the 1815 Up and Down is just an 1815 with the addition of a power reserve display, you are wrong. The watch is very different from the "classic" version. First of all the case is smaller: 39mm vs 40mm. Secondly the case doesn't have the same shape: look at the bezel which doesn't strictly extend the case side.
An more important: the movement L051.2 offers a larger power reserve (72 hours) which justifies the power reserve indicator.
Do you remember the Saxonia Thin? Actually, this watch is more important than we may think at first glance. It is powered by a handwind movement with a new lay-out for a Lange movement: the click, the ratchet and the crown wheel are visible. The 3/4 plate doesn't overlap everything due to the objective to get a movement with the smallest height possible. The objective is different with the 1815 Up and Down because it doesn't tend to be a very thin watch (even if with a 8,7mm height, it remains a quite slender watch). I do believe that the most important here for Lange is to propose a movement which is visually different. Moreover the small planetary gear train of the power reserve indicator adds something more to observe.
Frankly speaking, I like this movement. It is in my point of view more enjoyable to watch even if some may regret that the purety of the 3/4 plate was not preserved. But at least, you don't have the impression to get the same movement than with the 1815 and you can own both watches without a feeling of deja-vu.
The 1815 Up and Down is available in 3 different material cases: WG - PG and YG. The WG is my fav version because I always prefered the blued hands with neutral colour cases.
I was also pleased to see that Lange kept the case dimensions within very reasonable limits. With 39mm, the watch is very elegant. The power reserve indicator brings the touch of originality which makes this 1815 one of my fav novelties of the Salon.
YG:
You will notice the end of the power reserve in red:










