John:
All years, inclusive, of 1913 through 1937. 1938s, 1911s and 1912s were made without coupons.
There are some exceedingly difficult years to find with the coupon attached. Leon used to own a complete run of Zeenut's with tabs. I currently have such a run, and know of a very small number of collectors that do as well. But you could go 5 years or more without seeing tabbed Zeenuts from certain years.
Marc
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