Yes - this is a new take on a Pommel - the part that screws onto the end of the tang of an epee, holds the French-type handle on, and serves as a counterweight for the blade. All previous pommels are basically tapered cylinders run on a lathe.
With a French grip, one is allowed to hold it anywhere along its length, but the tradeoff is less wrist-driven power than a "pistol" of orthopedic-type grip, vs. a couple of inches of extra reach and fencing with "absence of blade", i.e when the opponent tries to take control, the French-grip fencer simply evades blade contact, because manipulation with the fingers is faster than with the wrist. I've attached an image of the prototype I fence with.
Once the brass insert is melted into place, the fencer can then insert lead of tungsten shot, to get the exact balance desired for the epee - the other unique aspect - adjustable weight.

I think draft5-g2 may be just a bit too bulgy for the purpose, but I'll print it tonight and see how it feels. I think that the flare at the waistline is not going to work quite as well as the straight sides just merging smoothly into the dome. Needless to say this is very subjective, but I'm guessing the little finger won't fit quite as well on the bulge in 5-g2.

As to the 27.5mm - that is the diameter of the waistline where the cone meets the dome, and thus the diameter of the dome.
20mm is the diameter of the base.
The 15mm is the height of the solid portion at the bottom, which the (needs to be straight but dimensioned as at McMaster-Carr link) hole pierces.
Above the 15mm, the rest should be hollow, with 2.5mm wall thickness.

Getting real close. I'll do some test prints, and be back in the morning (we're shut down here in Portland, with an inch of freezing rain on top of 10" of dry snow).