Counterfeit Neumanns, especially the U87 and TLM 103, have become more common. A genuine serial number will be cleanly engraved or etched. If the numbers look crooked, uneven, or are merely printed with ink that can be scratched off, it is likely a fake.
If you are looking at a vintage Neumann, the serial number might also be printed on the internal chassis. To see this, you often have to unscrew the bottom bell and slide the housing off. Only do this if you are comfortable handling sensitive electronics, as the capsule is extremely fragile. How to Verify the Manufacturing Date check neumann serial number
With vintage Neumanns, the serial number tells you more than just the age; it tells you the "version." For example, early U87 microphones (the "i" version) have different battery compartments and output transformers than the modern U87 Ai. Counterfeit Neumanns, especially the U87 and TLM 103,
They typically respond within a few business days with the exact month and year the unit was shipped. If you are looking at a vintage Neumann,
For very old microphones (pre-1945), records may be incomplete due to historical events, but post-war records are incredibly detailed. Why Serial Numbers Matter for Vintage Gear