The design is loosely based on others I found online, with a blocky style and a clamp piece to grip the dovetail stock. I've got two pins holes for pins to keep the mini clamp aligned properly and a spot in the center for a small spring to make it easier when screwing and unscrewing your workpiece.
I initially went with a 30deg dovetail angle at the top to match a cheap dovetail cutter I found on Harveytool. But after doing some more research, I found another 1/8" 45deg dovetail endmill that will work much better for this purpose, allowing for a more standard cutting size if customers already have them.
Because this was a quick one-off prototype, I had to get creative with my workholding to prevent the use of soft jaws, which I was able to get the side pocket cleared out by using parallels and a block of plastic in the center of the dovetail to grip it enough to machine. I then probed each axis individually to find my work origin as there wasn't any specific place I could do a normal probing cycle.
I have two pieces left to make before I can start testing the design, and those are the small clamp piece and baseplate that the dovetail workholding vice sits upon. My goal with this whole system is to create a quick-change system for different vice work holding. Currently, I have the dovetail design already made, but I've got a self-centering vice in the works and some tombstone ideas for those who are doing production runs!
I decided to sandblast this piece, and I'm super pleased with the results! I plan to anodize the baseplates, either an orange or blue color, to make them stand out, but for the workholding vices, I will have the same satin finish to all of them. As it turns out, sandblasting may be the wrong way to go; it's super easy to scratch, and it shows up very clearly on the surface finish. I'm going to look into tumbling them or may leave the machine marks as is.
My time spent prototyping this piece and working on its design came out to 3:47:00, which brings my total hours up to 17:57:00. I'm getting very close to my 20-hour mark, and I don't think I can do the rest of it at that time. I'd say there is a minimum of 5 hours before releasing it to the general public. I'm still going to push for the 20 hours total, but there is no way I can do it that short of time.