The Mühle-Glashütte caliber SW 280-1, version Mühle is a Sellita SW280-1 automatic moonphase movement with a custom rotor and a “woodpecker neck” regulator.
The Sellita SW280-1 is a Swiss made movement, but the watches using the SW 280-1, version Mühle have Made in Germany on the dial. It is unconfirmed what exactly this implies, but it seems like a more transparent way of describing it would be a Swiss made movement modified and finished in Germany – if it is in fact a raw movement shipped from Switzerland then modified and finished in Germany.
The woodpecker regulator is also known as a swan neck regulator. It is a fine-tuning device that does not necessarily add performance to the movement itself, but rather helps the watchmaker make precision adjustments which can lead to better results with regards to accuracy. It is likely that the addition of the “woodpecker regulator” is part of what helps the brand qualify for putting Made in Germany across the bottom of the dial.
Although the Mühle-Glashütte watch containing this movement retails for nearly $3,000 USD (for the bracelet model), the brand’s product pages do not present any images of the movement, nor the caseback. There are at least 13 pictures, including one of the actual moon, but none of the “SW 280-1, version Mühle”.
There is an official movement page here with more information about the Mühle Version, but it only shows the top (dial side) of the movement as shown above.
The grade of this movement is unconfirmed since the brand makes no mention of it. Their movement page does have some bullet points about the finishing and modifications:
Woodpecker neck regulation and Mühle rotor
Characteristic surface finishes with blued screws, Glashütte solarization and perlage