I'd suggest a pair of rubber gloves.
Establish where the barrel connects to the section. It looks like the metal threads are closest to where the pen should separate. Make sure the pen's surface is dry. With the rubber gloves, grip the barrel as close to the section as possible.
Grip the section as close to where it should unscrew as possible. Hold the section still & while firmly turning the barrel counter clockwise.
Since the MB barrel is made up of several different components fitted (pressed? cemented?) together, please do not hold the barrel by its white resin body, but the threaded area. And. easy does it.
This may work for this beautiful pen. I often use rubber gloves when I want to change out screw-in nib units. With the gloves you tend not to get slippage. Every year I have to separate fly rod members in this way (though they are not threaded, but pressure fit).
Hope this helps. Congrats on a beautiful pen!
Edited by tinta, 25 December 2015 - 17:38.
*Sailor 1911S, Black/gold, 14c. 0.8 mm. stub(JM) *1911S blue "Colours", 14c. H-B "M" BLS (PB)
*2 Sailor 1911-M Burgundy/gold pens: 14c. 0.6 mm. "round-nosed" CI (MM) & 1.1 mm. CI (JM)
*Sailor Pro-Gear Slim Spec. Ed. "Fire",14c. (factory) "H-B"
*2 Kaweco SPECIAL fountain pens: 14c."M" "B",-0.5 mm & 0.7 mm stubs (PB)
*Kaweco Stainless Steel Lilliput, 14c "B" -0.6 mm. stub (PB)
*Montblanc 254, 14c. "BB" (1.1 mm?) flügelfeder factory stub