The Abloy Classic is a disc-detainer lock that require specalist tools to manipulate the discs 

The Classic uses between 5 and 11 discs that interface with a sidebar. Designed in 1907 by Emil Henriksson, it is distinguished as being the first disc-detainer lock design.

Classic models are easily identified because they use a half circle ("D" shape) keyway. The Classic works by using angled bitting cuts on the key to properly rotate discs.

The pick is inserted and rotated 90°; the angled cuts on the key rotate the discs in the lock.

If all the discs are rotated to the correct position the sidebar can fall into the true gates and the plug can be rotated.

The first disc (hardened steel) is always a 0 cut (90°). The PL3020 padlock uses a brass first disc.