https://collections.si.edu/search/record/edanmdm:nmah_1218385

Phyllis Diller's gag file appears to have been made of 16 standard three-drawer beige Steelmaster (Art Steel Company, Inc.) index card files which were stacked in two columns and enclosed in a matching beige external frame which was mounted on casters. Having overflowed the 48 available drawers, there was an additional 3-drawer file added on top as an expansion.

The Smithsonian dates the files from 1962 to 1994, but perhaps the digitized version can be searched by date to determine the actual earliest and latest dates on included cards as most had at least a month and a year.