A "can of worms" typo. Any date in the last millennium could have been keyed in using the lower case "L," rather than the "one" key.
Before you run these searches, be sure that your automation software will search the copyright date.
This problem may show up in contents and summary notes, also. And that's where you're most likely to find "L066" or "L492."
I hope catalogers didn't make many of these mistakes by the 80's and 90's!
Searches can be truncated to:
L0+ ("ell" "zero" and truncation symbol)
L1+ ("ell" "one" and truncation symbol)
If that brings back an overwhelming number of hits, narrow it down like this:
If you're interested in searching for "L" inside a date, you might be able to find them by searching 0L, 1L, 2L, 3L, etc. Your mileage will vary with your automation software and your ability to customize reports.
This searching can be very tedious. I have let volunteers do the searching, listing the typos and giving the list to me. Then I make the corrections. Whether or not that works out depends on the abilities of the volunteers. Because SIRSI uses the dollar sign for truncation, I'm very careful about explaining truncation.
Count on many false hits. Again, whether or not a volunteer can spot the false hits depends on his or her training and education.