What is the easiest way to check the health of coilover dampers without removing them from the car?

To cut long story short, the local council has kindly decided to resurface a section of road on the brecon beacons, not so kindly theyve decided to leave massive unmarked tumps the size of medium sized speedbumps in random places all along the section. I was driving at about 20mph and hit of these and it didnt feel good.

Now I have a very faint rattling from the driver side wheel arch - might be unrelated but I am prone to paranoia.

Ive had a torch under the arch and nothing looks bent or damaged, and there is no oil/ gunk on the coilover unit around the damper road.

Ive done the "press down and see if it rebounds trick" but as coilovers are stiff its not very easy to notice anything.

Any ideas?

Ok had a closer look and there seems to be some grease up inside the dust cover when jacked up but this looks like the copper grease I applied to the threads when I first got the coilovers. I ran my finger around the base of the damper rod where it goes into the strut and there is no oil built up there.

Though it does seem easier to press down and rock the drivers side than the passengers?