One of the most extraordinary and exclusive fountain pens ever made, the Montblanc Meisterstuck Solitaire Royal LeGrand, aka the legendary Diamond Solitaire, is expected to fetch up to $175,000 at Bonhams & Butterfields sale of Fine Writing Instruments in Los Angeles on May 23.

The Diamond Solitaire caps a collection of over 200 extraordinary fountain pens, chiefly Montblancs, included in the stunning sale. Set with over 4,600 brilliant cut white diamonds over an 18 karat yellow gold barrel and cap top emblem composed of seven diamonds, the Diamond Solitaire was made to order in limited quantities and is one of Montblanc's most exclusive creations.

One of the world's most expensive writing instruments, it is extraordinarily rare and almost never seen at auction. Another top item of the May sale is a Montblanc Sir Winston Churchill fountain pen, the last of only 53 produced. Churchill famously preferred Montblancs and used them to sign many documents of great importance.

Fashioned of 18 karat rose gold inlaid with tortoise shell lacquer bands, along with a cap top ringed with 53 diamonds, it's a fitting tribute to the great statesman, estimated at $15,000 - $25,000.