Geezer,I don't think Sears made much of anything. They rebranded the products of other manufacturers. Often,very good ones.
Of the potential "Dremel on steroids" tools,off the top of my head,I can think of three.
The Makita 1/4 in die grinder,the Milwaukee,and the DuMore. I'm sure Bosch and who knows else have offerings.
I have a Makita because at the time it was less than 1/4 the price of a DuMore.
I don't use it a lot,but its still good.Its about like a big Dremel.
IMO,the dividing line is a two piece clam shell plastic injection molded body.
Whatever bearing behind the chuck is loaded in a molded pocket in the housing and the two halves are screwed together. Not my favorite system.
A metal tube handpiece with a bearing at each end and a spindle through the middle works in applications from truck axles to surface grinders to a Bridgeport to a Foredom handpiece, It can be rigid and run true. Years ago the DuMore was around $400. Probably more,now It was the standard back when "Head Shop" meant porting and polishing ,valve jobs,and a flow bench.
Here is the thing about rigidity and bearings. You put in a mounted grindstone. Dress it on a diamond or carbourundum. Its running true.
Touch the workpiece,it stays in full ,smooth contact. If your spindle is not rigid,that tool vibrates. Goes eccentric. It does not stay in full contact. It wheel hops.One part of the wheel contacts the workpiece,then it jumps off. Its like dribbling a basketball.Any motor vibration aggravates everything. The part of the wheel impacting the workpiece breaks down.Now its an out of balance cam. Results are bad.
DuMore is old tech. They made tool post grinders for lathes..They knew how. t cost money.
The motor in your hand..is a bit clumsy,adds heat,but worst it adds some vibation. Air motors can be light,have good bearings and run true and cool.
And make a lot of noise
Flex shaft tools isolate the motor vibration and weigt. Flex shafts have RPM limitations and you are tethered to a bench.
Another option is the Olde School dental engine..picolo arm,long cord "belt" driving the handpiece. Those are actually nice to work with.
My mold polishing mentor sold me a tool he put together. Is a Foredom type flex shaft tool. A 1/2 Horse 10,000 rpm motor drives it . That connects to a flex shaft..a heavy duty one bigger than Foredom The handpiece is like a Foredom,but a fixd 1/4 in Collet. Reducer collets work with that.I can put in a 1/8 in reducer. But more likely,I'd set that tool down and pick up the Foredom.
The big tool was mostly used with 1 inch diameter Tampico end brushes and diamond compound.
Also felt buffs. In the 1990's,a square yard of rock hard 1 in thick felt was about $900. We'd hole saw out a 2 in or 3 in or 4 in buff as needed.We'd mount those on a mandrel and use them with diamond compound,also.
I also had a tool called a "DME Profiler" or "jigger" Flex shaft . It was a variable stroke,pistol grippedreciprocating tool . 0-14.000 strokes per minute,used with stones,or laps.
These tools hung from a post,or "tree" mounted at the right,front corner of the bench. The active tool was selected via a bench mounted switch,and all were controlled by a big,yellow,industrial grade foot variable speed controller
on the floor.
A big,illuminated magnifier arm could be swung into play as needed
As working hunched over can cause great pain from the shoulder blades through the neck, I made a "podium" like stage of ply for the bench to rest my workpiece on. I could work sitting up straight.
With that I had a 6 in round magnetic chuck and a drill press vise to fixture my work.
I fitted a bread loaf pan with a lift off lid and a 1/4 in mesh screen false bottom,maybe 1/4 up,to be my stone pan. It was kept about 1/2 full of kerosene. Thats where my used polishing stones lived.
Just thought I'd share some ideas about a workstation where these tools were used.