In the 'Seinfeld' episode 'The Rye', what type of bread is stolen?

In the Seinfeld episode "The Rye," the stolen bread is a marble rye.

The story begins when Frank Costanza brings a loaf of marble rye to dinner at the home of Susan's parents. Because the Rosses never serve it, Frank takes the bread home with him. George worries that the slight will damage the relationship between the two families, so he decides to replace the loaf secretly.

Jerry and George return to the bakery, but an elderly woman named Mabel gets the last marble rye. Jerry tries bribery and emotional appeals, but she refuses to give it up. He eventually steals the loaf from her, creating one of the episode's most memorable comic crimes. The plan to deliver it to the Ross apartment then becomes increasingly elaborate, involving a hansom cab, a fishing pole, and an attempted toss to George's window.

Marble rye is a rye bread characterized by contrasting light and dark swirls, usually made by combining light rye dough with darker rye dough. The episode's bread was not pumpernickel or ordinary whole wheat; the specific joke depends on the coveted loaf being a marble rye.