If you do some searches on Montblanc, you will find that pen aficionados are not big fans - the quality is really poor. They do brilliant marketing, however.
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And the limited edition writers' series pens (like the Agatha Christie and Hemingway, etc.) used to be made for them by Bossert and Erhardt - better manufacturing. Some, however, are still quite poorly crafted, with the resin cracking near the nib sections, leaking, etc. It's especially worrisome with limited edition pens because replacement parts are also limited...