This example shows both W. Germany and an AB serial number dating it to early 1991 production. Nib and feed are correct for an early 90s pen - I don't believe it's ever been tampered with.
It's hard to get an exact nib size, but comparing it to other Montblanc nibs it looks like an Extra Fine. You can judge for your self based on the nib comparison photos (the nib from this pen is the finest one), and the writing sample paper was Rhodia and all pens were filled with MB Mystery Black, except for the medium Mozart which had Oyster.
Oyster is a dryer ink, so the Medium is writing finer than with Mystery Black. Here's your chance to get a nice example of an interesting 146 in a popular nib size. The item "Montblanc Meisterstück 146 Fountain Pen Black/Gold Extra Fine 1991" is in sale since Thursday, July 23, 2020. This item is in the category "Collectibles\Pens & Writing Instruments\Pens\Fountain Pens\Montblanc". The seller is "phillipjretro" and is located in Tucson, Arizona.This item can be shipped to United States, Canada, United Kingdom, Denmark, Romania, Slovakia, Bulgaria, Czech republic, Finland, Hungary, Latvia, Lithuania, Malta, Estonia, Australia, Greece, Portugal, Cyprus, Slovenia, Japan, China, Sweden, South Korea, Indonesia, Taiwan, South africa, Thailand, Belgium, France, Hong Kong, Ireland, Netherlands, Poland, Spain, Italy, Germany, Austria, Bahamas, Israel, Mexico, New Zealand, Singapore, Switzerland, Norway, Saudi arabia, United arab emirates, Qatar, Kuwait, Bahrain, Croatia, Malaysia, Chile, Colombia, Costa rica, Dominican republic, Panama, Trinidad and tobago, Guatemala, El salvador, Honduras, Jamaica, Antigua and barbuda, Aruba, Belize, Dominica, Grenada, Saint kitts and nevis, Saint lucia, Turks and caicos islands, Barbados, Bangladesh, Bermuda, Brunei darussalam, Bolivia, Egypt, French guiana, Guernsey, Gibraltar, Guadeloupe, Iceland, Jersey, Jordan, Cambodia, Cayman islands, Liechtenstein, Sri lanka, Luxembourg, Monaco, Macao, Martinique, Maldives, Nicaragua, Oman, Pakistan, Paraguay, Reunion, Uruguay, Russian federation.