Why did Mr. Otis offer the jewels given by the Canterville ghost to Virginia back to Lord Canterville?

In the story, the Canterville Ghost gave Virginia a box of jewels before he died.

Upon Virginia's return to her family, she presented her father, Mr. Otis, with the box of jewels. Later, however, Mr. Otis offered the box of jewels back to Lord Canterville because he felt that the priceless gems rightly belonged to the Canterville family, rather than his own. As a simple man from a working-class background, Mr. Otis did not feel that he had a right to lay claim to what was obviously his aristocratic counterpart's property. Additionally, the gems were of "great monetary worth, and if offered for sale would fetch a tall price." To Mr. Otis, it was quite clear that the jewels were Canterville heirlooms, and he wanted to return them to their original owners.

The only thing Mr. Otis requested was that Virginia be allowed to retain the box the jewels came in. Despite his surprise at a child of his "expressing sympathy with mediaevalism in any form," Mr. Otis felt compelled to speak on behalf of his beloved daughter.

For his part, Lord Canterville refused to accept ownership of the jewels. He assured Mr. Otis that Virginia had rendered his "unlucky ancestor, Sir Simon, a very important service" and that he and his family were indebted to Virginia for her "marvellous courage and pluck." Also, Lord Canterville proclaimed that, if he were heartless enough to take the jewels from Virginia, the Canterville Ghost would no doubt "be out of his grave in a fortnight..."

Additionally, since the jewels were never mentioned in a will or legal document, Lord Canterville maintained that he had no more claim on the jewels than anyone else. So, this was how Virginia came to retain the jewels and to wear them on the occasion of her marriage to the Duke of Cheshire.