This is a Brittex covered britannia B-3. REL subs are my favorite -- I have 3. Very articulate, very low, lots of flexibility for cross over and volume adjustment. I particularly enjoy, for music, the separate speaker level input. It allows sending full spectrum signal to the B-3, just like to the speakers. THen REL's excellent filters take out all the high stuff, and leave you with great, musical low end.
This B-3 works extremely well. It has 3 impressions on the right side, shown in the photo. They are about the size of a screw head. I believe it once sat next to something with screws, but that was before my time with the unit. It doesn't bother me because subwoofers aren't meant to be a bit out of the way! The front of the unit is an 8, the right side is a 6.
Sorry for the relisting. I made an error with the earlier listing. Also, I've had some problems with photo upload. It's not working right now. I'll add them later