这一典故在日本收藏家今井今朝春(KESAHARU IMAI)所著的ZIPPO系列丛书ZIPPO MANUAL第一册中有详细说明,原文说明如下:
In 1979, an error was made in the date code. One of the slash marks was removed from the left of the ZIPPO trademark instead of being removed from the right; thus the code / ZIPPO //. This code error was corrected within the same year to read // ZIPPO /.