The cup Johnny's mother passed on to him combines the two other important images in the novel: it is made of silver and engraved with the rising eye. The cup represents different things at different times, and Johnny's feelings about the cup show clear shifts in his character:
As a small child he had thought it was the most beautiful thing in the world. It was the reason why he had begged his mother to apprentice him to a silversmith (and there were none in Townsend, Maine). Now he was more critical of the cup. He thought it too chunky. (1.6.4)
The cup of the Lytes led Johnny to what he believes to be his life's work, but now he is critical of it, just as he is critical of Merchant Lyte and Miss Lavinia—from a distance.
The cup's next appearance is as a harbinger of hope. Johnny believes it will prove his relationship and inspire the Lytes to embrace him into their family. "There on the sideboard were standing three cups. They were identical to Johnny's. Silently he took his from its bag, set it with the other three, then stood back to look at the silken, bejeweled, perfumed folk crowding about him" (4.3.21). Of course, this hope is dashed when Mr. Lyte has Johnny arrested for stealing the cup.
When the cup is returned to Johnny after he wins his trial, he tries to sell it to Merchant Lyte. He's still trying to get something out of the cup, and to get something out of his family. And then Mr. Lyte steals it from him: "Johnny put the cup back in its bag, but before he could tie the strings to his belt Mr. Lyte's long fingers had reached out and taken it" (5.1.16). It's at this point that Johnny finally seems to realize the Lytes are totally bad news.
He doesn't see the cup again until he accompanies Cilla to the Lytes' country house almost a year later:
On the side-board, as yet unpacked, stood the four standing cups of the Lytes.
"Which one is yours, Johnny?"
He looked them over carefully. Only a silversmith could have told them apart. The base of one had been ever so little bent and straightened again.
"This is my cup."
"Take it now."
"No." He set it down and turned restlessly to Cilla. He could not say to anyone what went through his mind—not to Cilla, not even to himself. He acted and spoke blindly.
"It's no good to me. We've…moved on to other things."
"But it isn't stealing to take back what Mr. Lyte stole from you."
"I don't want it."
"No. I'm better off without it. I want nothing of them. Neither their blood nor their silver…I'll carry that hamper for you, Cil. Mr. Lyte can have the old cup."
"But your mother?"
"She didn't like it either." (8.2.15-27)
Johnny's ultimate rejection of the cup is symbolic of his rejection of the Lytes and all they stand for.