第四部分是口花标。口花标也叫税花标、封口标，多用在卷烟盒装封口处。口花标由民国时期的卷烟印花税税花演变而来。早期税花标有税务登记标识，现代口花标则以标注制造厂地、标注内装烟支数量者居多。
http://www.sh-tobacco.com.cn/main/ActionInfoOut/getDetail?id...

A picture of it here: http://bbs.my0511.com/bbsatt/day_080312/wubN1Q==_9h9YQsBXKzv...

One more: http://qkzz.net/magazine/1005-3964/2007/03/shca20070365-2-l....

Smokable articles such as cigarettes, cigarillos, or cigars are usually sold in rigid, semi rigid or soft packs . To indicate that the required tax has been paid for the smokable articles, such packs are often sealed with a tax label. Known tax labels for packs of smokable articles are made of paper or plastic material on which the required tax information is printed, both materials being substantially impermeable to light. Usually, the pack of smokable articles including the attached tax label is over wrapped with a transparent film. During the over wrapping process, certain areas of the transparent film are sealed together by the application of heat in, for example, a shrink tunnel
http://www.wipo.int/pctdb/en/wo.jsp?IA=WO2006069598&wo=20060...

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Note added at 12 hrs (2008-10-04 15:48:37 GMT)
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I am not 100% sure but this is the only thing I can think of.