...tabs &/or gutter actually increase catalog value, as it is option on printing sheet, where not every stamp/s have tab attached.
I know a lot of samples, not just from Israel, and a lot of countries, have this "practice" to print stamps.
Tabs & gutter, mostly, will give us more information about topic or "title" of issue.
I have samples from modern Bosnia (Serbian part), where they use gutter between, which is used in sheet of 8 stamps and on middle of sheet we have this gutter.
But other option exist in "attaching" tab to stamps, like, printing in sheets of 10, or in 5 set with gutter between (Serbia, Yugoslavia issues).
Michel catalog, list this option with different catalog value, and market value follow it too.
(shown: Republika Srpska issue from 2013 under topic "Brewery", where on this label You will see description, issued for factory in Banja Luka)

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