Researchers at the University of Buffalo (USA) have found that each 3D printer has its own unique "fingerprints" - minor features in the design of the object being created that are unique to this printer.
Scientists have documented that tiny "wrinkles" in each layer of plastic can be used to identify "a particular printer, filament size, nozzle, and other characteristics that cause slight variations in patterns." This technology is called PrinTracker.
This method is applicable primarily to FDM printers - in particular, to Makerbot, which uses long spools of filament to create an object layer by layer.
Since the printers used to print weapons are usually more complex and expensive, they may have fewer observable features - and more importantly, they are more difficult to recognize. But some parts still lend themselves to identification using new technology.