asphalt mixer: pre-adjusted and 'untweaked', so virtually ready-built for ease of use, the clue possibly lying in hervorragende Zugänglichkeit / outtstanding accessibility, rather than availability.

unverbaut : unworked (Bergbau, Ernst WB der ind. Technik).

un/verbaut - alas, as I know all too well - is ambiguous : un/developed as opposed to unobstructed / undistorted (verbaut can also mean wrongly built).