Before knowing whether a new product will really work, inventors often begin with a "Proof of Concept" to test and verify core technical assumptions before developing the product further. A Proof of Concept prototype may focus on only certain components of the product or the entire thing. It often consists of custom designed and fabricated components integrated with “off the shelf” and/or “sourced” parts to create a working functional prototype.
A Proof of Concept prototype provides valuable information early in the product development cycle, helping product owners understand whether their product will function as intended and decreasing the risk of failure later in production. It is not intended to be the final design.
A “Production Ready” prototype, in contrast, looks and functions much like a finished product. It's generally comprised of custom-designed and sourced components integrated to create a unit intended for volume production. The design contains all the information necessary to manufacture the product in volume. The prototype is built to as closely represent the production level product as possible and tested for “form, fit and function”.
Depending on the product you are manufacturing, you may need both types of prototypes in your development process.