Instead, Jack's introduction to Gwendolen is based on his assumed qualities:
* His name: Jack introduces himself as Ernest, a name he uses to live a double life in London. Gwendolen is instantly smitten because she has "always been a little bit in love with the name Ernest."
* His "wickedness": Gwendolen is attracted to the idea of a man who is "wicked" and "unconventional," and Jack plays into this perception.
* His "seriousness": He tells her he is very serious about marriage and is ready to settle down, despite his double life.
The irony, of course, is that Jack is actually a very conventional and respectable man, even if his behavior is somewhat unconventional. Gwendolen is falling for the persona he has created, not the real Jack Worthing.
Therefore, it is not a physical object or tangible quality that Jack gives Gwendolen, but rather an illusion of who he is.