Armored vehicles go through a long process from inception to full production. Vehicles can stop at any stage of the process, indeed few proposed vehicles actually make it to production. Many factors work against new vehicles. Sometimes a better vehicle design comes along; sometimes the technology does not exist to make the vehicle work. Shortages of raw materials, skilled workers or production facilities often stop projects from going forward. Sometimes the perceived need to for a specific vehicle passes away or the war ends and production no longer seems necessary. Occasionally testing will show a vehicle to be unreliable or impractical or technology will advance and a vehicle will become outdated before it enters production.
Vehicle Production Process:
Proposed: Vehicle type is suggested for production, no actual work is done on it. Panzer III with Panther turret.
Sketched: Vehicle is drawn in an artistic fashion to demonstrate the appearance of the proposed vehicle. Panzer III with Panzer IV turret.
Drawing: Technical, industrial drawings and blueprints are prepared to facilitate manufacture.
Model: A scale model of the vehicle is prepared to show the vehicle in three dimensions.
Mock up: A full size model of the vehicle is prepared, usually in wood or soft metal to demonstrate the drawings are correct and test fit of components.
Prototype: One or more vehicles are produced, often by hand, to validate the blueprints and for testing, usually fewer than three are produced. Panzer III with interleaved suspension.
Pre-production: One or more vehicles are produced to prepare production techniques and for testing, usually fewer than ten are produced. Early Panzer III with early suspension.
Limited production: Vehicle does not enter full production but is manufactured for testing a concept or as an interim vehicle or at the end of the war for peacetime use, usually fewer than 100 are produced. Panzer III as flame thrower vehicle.
Full production: Vehicle is manufactured in large numbers for field use by the troops, usually more than 100, often thousands are many in many versions. Panzer III in several series.
Remanufactured: Vehicle is returned to the factor for an upgrade. Panzer III upgraded with the short 75mm cannon.
Unofficial Field Modification, units modify a vehicle for their own needs, often based on a damaged or captured vehicle, only rarely more than one to take advantage of limited resources. Panzer III bridge transporter vehicle.
Official Field Modification, vehicles modified by the factory, or by kits issued by the factory, often lots of variation, sometimes hundreds are produced. Panzer III munitions carrier.
Probable vehicle: A vehicle for which there is some evidence but that has not been confirmed as having been produced, usually not very many; fewer than fifty are produced, if any. Panzer III flak vehicle.
Notional, vehicle that could have been manufactured, but for which there is no evidence that it was manufactured, perhaps could have been made into full production; often not produced because other better vehicles are available or does not fit doctrine or too expensive. Panzer III as an armored personnel carrier.
Fantasy, vehicle that was not and could not have been manufactured, production was never intended or technology did not exist at the time of the vehicles manufacture. Panzer III as a walker armed with a laser weapon.