While the "1" designates 1981, the "L" is not December. We see lots of Bianchi that turn up with an "M" and enough with an "N" to suggest that they're legitimate and not some factory error. Unlike several other manufacturers, Bianch doesn't skip the letter "I" either. While the exact meaning on the"L" is unknown, it does appear to be from late enough in the calendar year to represent the upcoming model year.