"Over the years, we've obviously had hundreds of windows," said Mike, who also runs the Onesti's Wild West Town next door to the auction house.
"People say, 'Well, how do you know it's a Tiffany window?' If you see a Tiffany window, you know it."
From wavy glass to evoke the quality of fabric to the layering of glass piece in a technique called 'plating,' the windows are indicators for Tiffany's attention to detail. On one panel, several men's beards even have tiny grey hairs.
The windows were made by the master craftsman in 1880 for the St. James Catholic Church in the South Side neighborhood of Bronzeville.
St. James was destroyed by a fire in 1972, but the Tiffany windows had been removed for repairs and were not part of the wreckage. The architect in charge of rebuilding purchased the windows to help fund restoration at the parish.
For the past 50 years, those windows have sat in a north suburban garage awaiting rediscovery.
"They were stored just piled on top of one another with a truck capper top on top of them and the elements have just destroyed the other windows," Randy said. "But thank god these two have survived."
Each set of windows is expected to sell for $100,000 to $300,000. After two months of repairs, the windows are still in need a buyer with "deep pockets" for full restoration. Everyone involved hopes to see the windows stay in Chicago.
The two-day auction will be next Friday and Saturday, Nov. 15-16, with the windows selling during the first night.
Check out some of the other items that will also be available at this auction: