“””I’d think the ballot envelopes are long since destroyed in all these states.”””
I believe most states have laws on the books requiring that ALL documents for an election must be kept for two years after an election.
Here are the laws in Michigan regarding retention of voting documents-—
300 Absentee Ballot Envelopes Until the election is held + 2 years
301 Absentee Voter List Until the election is held + 2 years
302 Application for Absentee Ballot Until the election is held + 6 years
303 Applications to Vote Until the election is held + 6 years
304 Affidavits of Identity Until the election is held + 2 years
305 Affidavit of Voter Unable to Meet Photo ID
Requirement Until the election is held + 6 years