@Cheese I have about 6 of the older one pictured in 24" and another 6 or so of the newer same size. I wish they were all the newer style but I just learn to work around the clamp head dropping on its own. I just last week cleaned all of mine up, waxed the bars, and lubricated the metal bits inside the clamp heads. They are smooooooth.

In the old shop, before the fire, I had a few year's worth of collection. I had the old style, which were thinner and didn't have the black sliding covers. They had the wooden handles too. Then the next version still had the same body, but plastic handles. After that were the Revo with the wider body, covers, and the stand-offs for the bar.
The problem that I ran into is that the extra width means they won't fit in a lot of the commercially made storage racks. The slots are too close together and they bind.
The only ones I have found that work are sold by WoodCraft stores under the brand WoodRiver.