Disk-Master 1050 by Stefan Wachter, apparently released on 1986 in Germany. The manual being in German I'm not 100% sure about the exact capabilities, but basically it is an editor for producing custom disk formats using an enhanced 1050 drive. The copy I've seen is for the Happy 1050, but if I understand the manual correctly, there is also a version for the Speedy.
It uses a very special copy protection method. It is in enhanced density and a handful of tracks have a sector numbered #27.
There are not too many disk copy protection methods for the Atari 8-bit. The possible methods are limited by the low level capabilities of Atari drive. A protection must be able to be checked and detected on a standard stock drive that is the one that the user has. The mentioned protection using tracks with sectors #27 can't be detected on a stock drive. Standard firmware on Atari drives ignore completely any sector number beyond the normal range according to the density. There is no way to check if such a sector is present or not and then the protection can't be verified. At least not in a standard drive. But this particular title doesn't run on a stock drive, it requires a Happy. It is then not bounded by the limits of standard Atari drives. In theory, very advanced and exotics protections are possible.
This is the 4th title I've seen that uses a special protection that targets an enhanced drive. The other three are all Archiver variants. I've been told there are a couple more also released on Europe.
It is also interested how exactly the protection is verified. The software first "programs" the Happy and installs a custom command table. It then issues one of the custom commands that attempts to read all the sectors #27. If the command fails for some reason, the software, obviously doesn't run. It is not too difficult to bypass the protection check performing a quick crack. Then the program continues, the menu is displayed and the software is operational. But when the custom command reads those special sectors, it doesn't just verify that they exist. They are all read into Happy's extended RAM and they include most of the in-drive custom code that it is required for actually producing a custom format. So the quick crack will fail when at that point.
The software might be able to copy itself. Or at least it might be able to produce tracks with sectors #27. May be it can create such tracks but not write those sectors. Don't know for sure. Again, the manual is in German so I'm not sure exactly about its capabilities.