I have the old Model 44 Solid Steel rack, which was later renamed the 5.4. Those were the Solid Steel racks, long-ago discontinued, with shelves that each sat on three aluminum cones, the tips of which sat in little wells in the cross-members of the rack's aluminum frame. Each shelf is 3/4" MDF covered with a thin veneer of Formica. MDF is out of fashion, but I guess the stock shelves could be replaced with maple ones.
The metal frame is nicely made and finished, and the four corner pillars can be filled with sand/lead shot/kitty litter. Each pillar has a nicely-machined stainless steel threaded spike in it's bottom for leveling. The only problem I have had with the rack is that the top shelf sits on three cones, the one in the back in the shelf's center. My turntable, which weighs 60 lbs. and has four feet, was heavy enough to bend the back side of the shelf at it's two corners---since it was supported only in it's center, all the way down onto the top of the pillars. I removed the three cones and placed the MDF shelf directly onto the four corner pillars. Cones are reputed to provide isolation, but I don't buy it.