I presume this is to prevent entry. It is very easy, with a 3 lb. slege hammer to smak the doorknob off, shove a screwdriver into the center shoving out the shaft and pulling the locking assy. to open the door. Code? I'd think not.
IPVMU Certified | 04/14/14 01:43am
The escutcheon around the knob is there to keep vandals from smacking the knob lock off the door with a sledge hammer or sticking a piece of pipe over the knob and prying it until it breaks open.
If it is an egress door, it absolutely is against code. If it is a storage closet, it probably isn't.
This looks like some version of a "knob guard", possibly home-made. These are typically installed on gates where it is possible to reach through the gate opening from the outside to operate the knob or lever. If you install a knob guard, it makes it a little harder to reach over or through the gate to grab the knob. Unless your door is right next to a gate or fence, I don't think that this is the purpose of the guard here however.
A fairly common burglary technique is to use a large pipe wrench on cylindrical locks such as these. This creates a tremendous amount of torque on the lock body and the door usually pops right open. I suppose that this ring would proviode some degree of protection against this type of attack.
Seen it before. Attempts to prevent someone with a pipe wrench twisting the entire lock to gain access.