Usually that translates into 'just back from factory service'. It sounds nicer to say check up than service, because a buyer may be more leary of buying a piece of equipment if it had a 'break down' history. In my experiences costlier gear does have more breakdown time. Most Sony receivers will not break for at least a decade, while a preamp or amp that cost 50 times as much probably will need some service in that time. Service because it's not working. From a seller's POV, check-up is a more marketable term than service. I don't believe in this sales technique, and I shy away ads with such claims.
Regards,
John
Regards,
John