I made myself a present for Christmas... and I've just opened it
It took me hours to figure out I had to use much force than usual to set the pins.
I couldn't pick it until I tried this: after opening it with the key, I left the arc open and turned back the cylinder. Then I could pick it with almost no force on the wrench.
After this I tried again with the arc closed and it required much more force to set the pins and pick it.
The code written on the envelope is M5DLH, I couldn't find any info about it. I know it has 4 pins, I think there aren't any security pins.