The phrase "a prototype of their" is correct and usable in written English.
It can be used when referring to an initial model or example created by a group or organization to test or demonstrate a concept or idea.
Example: "The engineers presented a prototype of their latest electric vehicle at the conference."
Alternatives: "a model of their" or "an example of their".
In November 2009, they opened a prototype of their cafe in Mr. Mazzei's Upper East Side apartment.
Whether it is to hire a great, new developer, create a prototype of their world-beating product, or simply to pay for their lunches.
They maxed out their credit cards buying gadgetry, set up shop in Carr's room, and by summer had a prototype of their product up and running.
Gans & Jelacic, a firm in New York, built a prototype of their entry, a triangular structure that pops up from a container with the help of a standard car jack.
Vibram, an Italian sole manufacturer, unveiled a prototype of their Five Fingers shoe (pictured), a glove-like slipper with individual toe compartments, at a trade show in Salt Lake City in 2005.
Just beyond the dining area are some of the couple's latest designs, including their round Curio table made from coffee-tree wood and a prototype of their Calibra sofa for Bernhardt.
At the moment, the Canada-based AppSeed team have a functioning prototype of their app but are looking for a funding bump to turn that into a fully fledged iOS app (with an Android version planned as a stretch goal for the crowdfunding campaign).
By the end of the conference, they even had a working prototype of their idea in place.
The team still has to make a working prototype of their waveguide, which physicist Neil Broderick of the University of Southampton, United Kingdom, points out will be tricky using existing technology.
Often, early-stage companies have little or no revenue, inexperienced management teams and perhaps only a rough prototype of their product or service.
These contestants will be provided with a free-of-charge SPARK Your Imagination kit based on the VIA ARTiGO Pico-ITX board to build a working prototype of their idea.
