You could very easily tell by literally any of the other tech in the house. Roombas, Solar panels, space heaters, electric car. Or even by the the general utensils, encyclopedia, flooring, type of heaters.
Besides computers have changed the world just as much in the last 40 years as we have moved from horse carriages to cars, if not more. Just because it didn't require retooling of cities doesn't mean it isn't a giant leap.
Also the lack of certain things would be an indicator. No home phone. No phone books. No physical maps. Less likely to have a dictionary or other books. Fewer newspapers and magazines.
Besides computers have changed the world just as much in the last 40 years as we have moved from horse carriages to cars, if not more. Just because it didn't require retooling of cities doesn't mean it isn't a giant leap.