Celica/curren Coilovers Help

[hm.clark]

Hey all,

I bought a 2nd hand set of full coiovers about six months ago and i just got round to installing them the other day. I now however have a knock coming from one of the coilover units, in the back right. I was wondering if there is a process of elimination i can go through to determin if its just the pillow ball top mount or if the whole shock is gone. My other problem is that the coilovers are second hand. there are no stickers or part numbers on the unit anywhere to try and establish a brand, bar a logo on the adjustment dial which is not familiar to me. I have included an image of the logo on the dial.
Any help is much appreciated.

[Old Red Celica]

Sure it's not an anti-roll bar or drop link?