I can't speak for the Mills cab, but I can speak for mine. The Scumback/Southbay cab is based on the 60's Marshall cab design which had more internal bracing for the baffle board, and casters. Differences are (but not limited to) the following. 1) They had pin type casters pounded/pressed into the bottom of the cab, and then into the baffle board triangular wood support, creating a stronger cab, and better vibration transfer. This equated to more low mids & low end tone capability, relative to the speakers installed. Caster base pics from a 68 slant: What I use in my cabs. They're actually slightly thicker than the old pin caster bases Marshall used, and have the four screw flange to screw into the wood, too. So basically it's a hybrid of the best features of both style casters Marshall used: Later models used bolted on caster bases that didn't extend the caster pin into the baffle board reducing strength/vibration transfer, etc. These later casters started in roughly mid 1970. I show what the later casters look like vs what I use in my cabs here at this thread: http://www.thegearpage.net/board/showthread.php?t=573045 2) Sound post and baffle board bracing. Sound posts were bigger in the 60's, where they actually used a larger 2x4 than today's standard 2x4 sound post bracing the baffle board against the back panel. In fact, Marshall has reduce the soundpost now to a 2x2 for almost all of their cabs. They started that in the mid 70's (76 IIRC). Slant cabs had much larger/more robust bracing that did a much better job of bracing the baffle board from flex/vibration. Here's what they looked like in 1968/69: Here's what I make, same exact thing: 3) I feel the wood used in the 60's was likely "cabinet grade" or 2BB, although it probably wasn't "furniture grade" (3BB) which is what I use to replicate that quality now. I've stripped and restored enough older Marshall cabinets to know that when you don't see any "football" type repairs that the wood was of higher quality in general. While there were some footballs in Marshall cabs, it was usually limited to 2-3 max per cab between all four sides and the back panel. I see that percentage in the 3BB baltic birch (furniture grade) wood. When I supplied stripped old Marshall cabs to my cab builder, he said the 3BB grade baltic birch (the highest) was what replicated that old wood the best. So I pay more for the wood used in my cabs. In fact, I use 3BB in all of my cabs now. 4) The basketweave (aka Salt & Pepper) grill cloth is thicker on old Marshall cabs than new ones, so it adds in more bass, and it takes a touch off the treble notes. In 70/71 Marshall switched to checkerboard cloth which is easily just 1/2 the thickness of S&P. Later on they switched again to just black cloth, which isn't as thick as original S&P either. The thinner your cloth the more highs get through, and your bass isn't as deep or rich sounding. I prefer the S&P cloth for this reason, no matter if you use M or H magnet speakers (G12M/M75 or G12H30/H75). 68 cab's basketweave (aka Salt & Pepper) cloth. Notice it fades over time. Fortunately Marshall still makes this cloth, it's just newer looking. Here's a pic of new S&P cloth on top of the old 68 slant cab cloth. You'll notice the weave/density/etc is the same. 5) Speakers...my thoughts are well known on this subject, but suffice to say that I think the late 60's/early 70's (pre 74) Celestion speakers were the best for rock tones, period. 6) Cabinet joints. Here's where my cab guy and I differ from Marshall. They used 1/4" finger joints. It's a decent joint, no doubt. You can slop a lot of glue in there and they'll last for years unless you drop them on a corner, or let UPS handle them. I've seen enough of the new Marshall Handwired cabs that had UPS damage them (or whoever) to know the finger joint isn't the strongest. I'm sure many of you have seen the Handwired cabs that had tolex split from the front corner edge to the back after being dropped. With that in mind my cab builder recommended that we use 1/2 blind dove tail joints that interlock. The new cab maker I have coming on board (due to increased sales) bitched up a storm about this. He had to buy a special bit/router to do it. It takes a lot longer to get a perfect joint, since it's tolerances are very tight, and if you screw up you scrap a nice piece of birch. So more care has to be taken to do these right. But with an interlocking joint PLUS glue, you'll be very hard pressed to get that cab joint to fail. Again, this takes more labor & skill to make, but it adds additional strength and vibrational transfer. Many players refer to this quality as "the knock" tone. That's the tone you get from a cab when you knock on it on it's top and it produces a deeper tone.