The CISA SP - Security Profile (is there another name for it?)
Basically it's a pin tumbler with a nasty keyway. Reminds me of an ASSA Twin I saw some time ago:
In addition to the keyway, this lock has 4 ball bearings (2 on each side) as a passive system to restrict keys.
Here's the plug:
On one of the sides (the second image) it only takes 2 ball bearings that are let inside the plug by 2 dimples on the side of the key. On the other side (the first image), the chambers are deeper, so it also has 2 pins before the ball bearings:
Here's the pin configuration for this one:
3 spools, 1 serrated(?) and a regular driver pin. The first key and driver pins are hardned for anti-drill protection. It also has 2 other anti-drill pins on the cylinder:
And here's the key, pins and plug:
As for the housing, it's not rounded from the inside. Any guess why that happens? The image isn't very good, but you can see the squarish shape of it:
Now off to picking it!