I have seen several dampners slip. The guy with the sharpie idea has it right. make sure that the mark goes from the timing mark down the front of the dampner all the way onto the hub of the dampner so you can see if the rubber layer is allowing the outer ring to slip. IF IT IS, GET A NEW DAMPNER! THIS THING WILL BE A GRENADE AT FREEWAYS SPEEDS!!!
I always run a FluidDampner on all my stuff. I hate buying radiators, water pumps, belts, air conditioner compressors, fenders, batteries, etc. just because I wanted to save a buck and use a worn out dampner.
The rubber on your dampner looks bad to me. It should be even all the way around, but yours seems to be pushing out in at least one spot.