Very interesting... I had seen this lock before, but I wasn't sure how secure it'd be. Playing with the simulator (http://toool.nl/images/e/e1/MhVisualizer_V2.0_p.swf), found in a link on the website bewoody provided, I'm still not sure I'd want to trust this to anything I truly value.

For example, UDL is the equivalent of LDL, and UDLR is the equivalent of LLR... but by extension it is also equivalent of LDLR. There are 5 positions for each of 4 tumblers, but not every tumbler position is valid, so the total number of combinations must be far less than 5^4.

I know that the dial combination locks have a reverse combination as well, and that the total number of tick marks is actually greater than the number of valid positions for the dial, but this whole system reminds me a bit of a game of lights out.