It is a state examination body that clears a relic — not the shop
Under the Ministry of Culture measure, the National Cultural Heritage Administration (国家文物局) is responsible for cultural-relic import/export examination and designates the 文物进出境审核机构 (examination bodies), which are jointly formed by the NCHA and provincial governments (Art 2–3). So the authority that decides whether your antique may leave is a government examination body, not the dealer's word or the shop's receipt.
Official source: Ministry of Culture and Tourism of the People's Republic of China (zwgk.mct.gov.cn) — Administrative Measures for the Examination of Import and Export of Cultural Relics (文物进出境审核管理办法, Ministry of Culture Order No. 42) (source adopted 2007-07-03, effective on promulgation; read August 15, 2026)