Mary Lincoln's engraved opera glasses?

[Susan Higginbotham]

"Mr Wright said there were 'at least two other pairs' of opera glasses supposedly used by Mrs Lincoln on that night."

How many pairs of opera glasses would a person typically take with her to the theater? I can see taking two pairs, perhaps if one had better focus than the other or Mary wanted to ensure that Miss Harris was provided for, but three gets rather unwieldy.