A man who marries a virgin is obligated to pay her 200 zuz in case of divorce or his death (as mandated by her ketubah, while a man who marries a widow or a single woman who has had sexual relations (not a virgin) must pay her only 100 zuz.
There was an incident with a man who married a virgin and obligated himself to pay 200 zuz. When they had sexual relations for the first time she did not have hymeneal bleeding. He went to Rabban Gamliel, son of Rabbi Judah the Nasi, and told him that his wife had not bled. In her defense, the wife claimed that she had been a virgin and was still a virgin. Rabban Gamliel decided to check whether she was indeed still a virgin. He asked that two gentile maids be brought to him, one a virgin and one not. He sat them on a barrel of wine with their naked sexual organs exposed to the wine within the barrel. After he sat them down he smelled their breath. He smelled the breath of the virgin and did not smell the wine, for her hymen blocked the passage of the smell from her sexual organs to her mouth. He smelled the breath of the maid who was not a virgin and smelled wine, for a woman who is not a virgin has no hymen to block the smell of the wine from traveling from her sexual organs to her mouth. After experimenting with the examination of the maids, he asked the Jewish woman who had claimed that she was still a virgin to take a seat on the wine barrel, with her sexual organ exposed to the wine. Rabban Gamliel smelled her breath and did not smell wine, so he concluded that she was speaking the truth and was indeed a virgin. He told the husband the results of his examination and authorized him to continue his life with the virgin love of his life, in his own words, “Go, be happy with your bargain.” The scholars asked: Why did Rabban Gamliel examine the maids? He could have examined the woman who claimed to be a virgin straight away. Answer: Rabban Gamlilel was not expert in this examination; he had been taught a tradition handed down from the days of the judges. It is written “And they found among the inhabitants of Yavesh Gilead four hundred young virgins, that had known no man by lying with any male” (Judges 21:12). The sages asked: How did the people of Yavesh Gilead know that they were virgins? Answer: “The people of Yavesh Gilead sat the virgins on wine barrels. If they had had sexual intercourse with a man the scent rose through their mouths, and if they had not, the scent did not rise” (Yevamot 60b). But Rabban Gamliel was not expert in this examination, so he did not want to examine the Jewish woman (and be unsure of his success) — it is not proper to belittle a Jewish woman thus. Therefore Rabban Gamliel first tried the test on the maids, to test his skill and the veracity of the test. After the first test went well, he examined the woman who was the subject of the dispute.
(Babylonian Talmud, Tractate Ketubot 10b)