Mine is a WM400, bought sometime in the '70's from either House of Holland or Argos, can't remember which. I've repainted it, added tape on the bottom of the legs to make the plastic feet a tighter fit, replaced two of the hinges with bolts (I seem to recall having make a pair of tubes or similar for the bolts to work), added a piece of 1/4inch wood, Ramin possibly, on the inside of the jaws and repaired one of the handles, the casting broke! And still it does all it's supposed to do.
I've bought various add-ons, the arms for holding large sheets, the steel bracket to convert it to a portable saw bench, the special bracket to allow the use of a tool tray on the rear of the rear jaw.
It's been used for just about anything I could cram into, or on, it: holding an old file whilst cutting it up, holding parts of tree branches whilst using a chainsaw, cutting smaller branches & scrap wood using the portable saw attachment, and right now it is being used as an extra table with a piece of plywood on top of the jaws and bits & pieces stored on top. In short, it's been one of the most useful pieces of equipment I've ever bought.
Mention has been made of "knock-offs", ie copies made by other than B&D. My daughter has a "knock-off", the design of which is so poor that the folding arms for the legs stick out rather than lay parallel to the legs as mine does. In other words, B&D may be more expensive, but it is proper engineered product.
Cheers,
Peter G. Shaw