Brassboard

DOD hopes during this part of Phase 1 to develop a sufficient number of integrated system brassboards.

Source: wiktionary

From the outset, the Army was interested in five of the six basic functional brassboards to be provided by the program.

Source: wiktionary

Brassboards generally represent a more serious attempt to mimic the behavior of the final product, particularly in terms of component placing, connector lengths, and packaging. Portions of brassboards that involve high-risk areas may be constructed as near replicas of the envisioned final product and may be of sufficient integrity to undergo considerable testing.

Source: wiktionary