7,000 may be low in comparison with, say, Firepower, but it's still a reasonable number. Bear in mind that Blackout was one of the games Williams turned to in the bleak pre Space Shuttle era, when the layout was used for Warlok. Though that may will be even scarcer, as ipdb lists only 412 produced. I must've been lucky (if that's the word) to see one in an arcade in Weymouth.
Despite the similarities, the later game's credited to a different designer, Mike 'Seawitch' Kubin, rather than Claude Fernandez.