As June gets up to leave the table, she tells Beaver "it's an heirloom [pronounced AIR-loom] ring". Beaver doesn't see the word written, nor is it spelled for him, but he asks Ward, "what's a HAIR-loom?", as if he'd seen its spelling and thought the 'h' was pronounced.
At the end, right after Beaver has read the letter and Ward is talking to him about it, a fly lands on the camera and then flies around and lands on Beaver's shirt.
After Beaver says the ring looks like gold and Wally tells him to try biting it, Ward says that won't be necessary because it's marked 14 karat. But at this point, Ward hasn't been close enough to read anything on the inside of the ring.
At the dinner table, June tells the boys that she received a letter from Aunt Martha. Wally and Beaver take a second to try to remember who Aunt Martha is before they conclude that she's their "umbrella aunt". In the first season, Aunt Martha played a significant role in two episodes: "Beaver's Short Pants" and "Train Trip". It is highly unlikely the boys would have to think twice about who Aunt Martha is.