Scarlett67 has it; the sentence can be read as passive (with the “were” omitted), but the 2nd and 3rd definitions she(?) gives indicate “sold” could be active. The situation is ambiguous since the past tense of “sell” and the past participle (used to form the passive) are both “sold”.
If English were a language like ancient Greek, I’d argue that as a stand-alone sentence (rather than “headlinese”) this is an example of the middle voice. This is the form of the verb where subject and object are the same; some tenses in Greek have separate forms for this specific voice alongside active and passive (for Latin scholars, there may have also been a middle voice in this language–it’s a good explanation for the existence of deponent verbs–but the forms were eventually assimilated with the passive).
English has some verbs I would characterize as middle voice. “To lie”, “to sit”, and “to rise”, for example, are the same as “to lay myself”, “to set myself”, and “to raise myself”. Based strictly on forms, one could argue e.g. “lie” is the middle-voice form of “lay”, etc. I sincerely doubt there ever was a strict middle voice in English, but these verbs are examples I use whenever I discuss middle voice with my beginning Greek classes.