Genuine Neumanns have the logo engraved or silk-screened in a specific location. On many counterfeits, the logo is a cheap sticker that peels off, or the engraving is shallow. Worse, some “franken-mics” are real Neumann bodies with fake electronics. In that case, the serial number is real, but the internal schematic is wrong. You must listen and test.
Low 3-digit or 4-digit numbers. Often feature "Berlin" or "Gefell" branding depending on the post-war factory split. check neumann serial number better