I've owned and used a Ridgid-Simplex 43 CP vise since 1976. The vise was nearly new when I got it as a used vise. My Simplex vise lacks one of the clamping dogs on one side, and the pipe jaws were not with it when I got it. I use a Ridgid 'tri stand' ( a folding 3 legged stand) with a Ridgid pipe vise, so do not miss the pipe jaw inserts. My Ridgid - Simplex vise has stood up to anything I have used it for, including hot bending of steel, holding work while I chipped it off with cold or cape chisels and hammers, cold bending of steel with a 3 lb hammer, and basic machinist's use- holding work for filing, tapping, and similar.
I believe Ridgid ceased to make that particular vise some time about the time I got my Ridgid-Simplex vise. Reason being that I have a new, never used Columbian vise which is a dead wringer for the Ridgid-Simplex vise. The COlumbian vise dates to about 1973 or 74.
There is another red herring in this matter: Simplex vises, or at least the Simplex name, was put on machinist vises made many years ago in Woonsocket, Rhode Island. Either the Simplex vise company of Woonsocket went out of business, and Ridigid picked up the trade name, or Ridgid bought the product line and trade name from them.
Ridgid is famous the world over for their pipe fitters and plumbers tools, mainly pipe wrenches. For many years, they had offered a line of pipe wrenches, pipe threading die stocks, and 'pipe machines'. Pipe Machines is a slang term for a powered pipe threading machine. Ridgid has offered a lineup of powered pipe threading machines for ages. They expanded the line as the years passed, offering powered sewer cleaning snakes, and tools for working with copper tubing (flare blocks, tubing cutters, tube benders).
It seems like in more recent years, Ridgid began offering things like portable generators, wet/dry vacuum cleaners, and fiberoptic pipe inspection devices. I am fairly certain Ridgid dropped the Simplex vises from their lineup many years ago. More recently, Ridigd began offering a German made bench vise with their name on it. It's a high quality vise with a n equally high price tag. Not up to the kind of heavy work that can be done in an old Ridgid-Simplex bench vise.
I think Ridgid was either a family-held or independent corporation for most of its existence. Again, in more recent years, I think a conglomerate (Emerson ? if I recall rightly) bought up Ridgid. This might account for the additions of things like wet-dry vacuums and portable generators to the product line. Ridgid has kept up with the times and changes in the plumbing world. They offer tools for working with the flexible plastic piping ("PEX") and a powered portable crimper for making up copper piping with crimp-type fittings rather than sweated joints.
The Ridgid-Simplex vise is a basic machinist's vise of a design that was kind of an accross the board thing with US vise makers. As the OP notes, there is a LOT of iron in a Ridgid-Simplex vise, as you would expect in any 'classic' US made machinist vise, whether it be Morgan, Yost, Parker, Athol, or Prentiss. The finish on some of the parts on the Ridgid vise is not quite up to the likes of a Parker or Prentiss vise, but overall, it's in the same league. Another sidenote: Ridgid has had a competitor in the manufacture of plumbers and pipefitters tools for ages in the form of Reed. Reed is in Erie, PA. Reed has offered very heavily built machinist bench vises for ages. A Reed vise is guaranteed to weigh a good bit more than many similarly sized vises of US make would weigh. Reed vises were known for being able to stand up to the worst abuse in places like powerplant maintenance shops, shipyards, locomotive backshops and similar.
Ridgid is alive and well in Elyria, Ohio. With the moves away from the threaded piping and away from cast iron soil pipe, Ridgid's product line has correspondingly lightened up. Ridgid would have offered the Simplex vise to shops and contractors doing commercial, power, or process piping. Those type customers would have pipefitters fabricating structural steel pipe supports or pipe hangers, often right at the jobsite. For that reason, a heavy vise like the Ridgid-Simplex would be needed, and would be a logical part of Ridgid's lineup. While this type of piping and the hangers and supports for it are still very much in use and being installed on new projects, Ridgid found reason to abandon the Simplex vise line. A pipefitter making up a pipe support bracket from structural steel would use a heavy vise and use it hard, often heating steel with a rosebud, and using a sledge hammer to beat the steel into the required bend while held in the vise. Seen it done MANY times on powerplant jobs, done much the same sort of thing in my own Ridgid-Simplex vise. My Ridgid-Simplex vise is mounted on a bench I made back about 1983. The legs are 1 1/2" standard weight black steel pipe, with 3" x 2" x 1/4" steel angle used for the top and mid-height cross members. Legs have 1/4" steel plate welded to the bottom ends. Top of the bench is 2" thick wood plank, edges planed and then pulled together and edge-glued. Heavy wood battens are lagged to the underside of the top. The top is carriage bolted to the steel angle on each set of legs. The Ridgid-Simplex vise sits on a piece of 3/8" thick steel plate that is "let into" the wood top and spans the full width of the bench top. 3/8" bolts are run up from the bottom surface of the planking, into tapped holes in the steel plate. I cleaned the projecting ends of those bolts off flush with a sharp cold chisel and hammer, not wanting to use an angle grinder in my basement, nor wanting to gouge the top plate unnecessarily with it. The Ridgid-Simplex vise is held to the bench with 5/8" diameter steel bolts. The vise is located close to the left end of the bench, so I can work with things like diestocks or bending work that might otherwise hit the top of the bench. The vise has plenty of scars on it, and Mea Culpa on that matter. I do have home made copper jaw caps for finer work, so the vise sees the whole range of work and does fine with all of it.