The Entity ID for a serial must always be the prefix "SN" followed by the 8-character ISSN for the title. Some older serial titles do not have ISSNs. In this case there are two options: apply for a retrospective ISSN, or assign a pseudo-ISSN.
The U.S. ISSN office will assign ISSNs retrospectively upon request. If the publisher is in business, the library must request the publisher to make the application. If the publisher no longer exists, a library can apply directly. UF’s Digital Library Center will apply for retrospective ISSNs on behalf of SUS libraries.
Pseudo-ISSNs should be entered in the 024 of the bibliographic record, to let other institutions know that the pseudo-ISSN has been assigned. The format of the 024 should be:
The first indicator is "7" and the second indicator is blank. The subfield "a" contains the string "sn0" (zero) followed by the NOTIS key of the bibliographic record. The subfield "2" contains "PALMM".
The string "SN0AAA1234" is then used as the Entity ID for the digitized title.