My only comments are that usually, and I may be wrong, is that Volvo supplied towbars normally have either a fixed swan neck, or are the detacheable variety. They don't have a bolt on version to my knowledge. However, a Volvo 'type' approved towbar may have such a fitting. This merely means that fitting it will not invaldate any insurance or warranty, not that Volvo actually supplied it. Companies such as Brink, Witter etc do supply extremely good towbars under this sort of decalaration.
I still suggest getting an expert opinion, before using anything that looks suspicious. One thought crossed my mind and that is the previous owner may have used the vehicle for towing something particular, an agricultural trailer for example and necessitated such a towhitch. This may not be suitable for the weight of a caravan.