Well I did have 3 derringers, but for some reason can only find the two plastic top caps and metal air flow ring, and not the actual build decks! I had a copper one installed on a small 18350 mech with a recessed top so the atomiser sits halfway in that I hadn't used in a long time so only had the copper one left.
I wonder why the copper one is prone to getting so manky? I am talking things were growing off the screws on the build deck manky! And they aren't even copper.
I've never had a Kennedy, one RDA I never got round to getting, not even a clone. I heard good things about them though and like the way they look with the bottom airflow.
This could well be what happened as well as the grime build up- I haven't actually changed the O-rings yet but have plenty of them from all the RDA's and RTA's I have bought (a lot of clones I must admit, although my favourites I do own the genuine ones and got the clones to compare).
They seem OK now, but if I find one a bit tricky I will try changing the O-rings out, thanks for the tip!