Short answer

306.104 is not a published A. Lange & Söhne reference for the Zeitwerk. The Zeitwerk family uses 140.xxx numbers, for example 140.029 and 140.032. A watch sold as a "Zeitwerk 306.104" carries a code that does not match the maker's catalog. Treat the listing as a replica or a mislabeled watch until the seller shows the caseback and the guarantee booklet.

Where the code comes from

Replica sellers assign their own stock codes. A code such as 306.104 looks like a Lange reference because it copies the same two-block pattern and the same six digits. Lange uses the first block to group a model family. The Zeitwerk block is 140 and 145. The second block marks metal and dial version. 306 sits outside that range.

Some listings pair a real model name with an internal code. Others copy a reference from a different watch. Neither case changes the physical facts. A Zeitwerk made in Glashütte has a case number, a movement number, and a paper trail.

Checks that settle it

  1. Read the caseback. A real Zeitwerk is engraved with the reference, the case number, and the metal hallmark. The engraving is crisp and filled.
  2. Look at the movement. The first Zeitwerk runs caliber L043.1, a hand-wound movement with a three-quarter plate, screwed gold chatons, and a hand-engraved balance cock. A replica uses a modified ETA or a Chinese clone. Its balance cock carries machine engraving.
  3. Watch the numerals. Zeitwerk hours and minutes jump. The discs snap at the top of the hour in place of a sweeping hand.
  4. Match the numbers. The reference on the caseback must match the guarantee booklet and the dealer invoice. Lange holds a service record for each movement number.
  5. Check the price. Pre-owned Zeitwerk watches trade in the tens of thousands of dollars. A listing at a few hundred dollars is a replica, whatever code it shows.

What to ask a seller

  • A photo of the caseback with the reference and case number.
  • A photo of the movement through the sapphire back.
  • The original invoice and the guarantee booklet with matching numbers.
  • The service history from Lange or an authorized service center.

A seller who cannot supply these items has no proof of origin. No reference number on a web page replaces that proof.