It could be residue from card printing.  Was a period added to the end of a spelled-out series tracing posted to the bottom of the card?

Mark K. Ehlert                 Alma: NA02
Cataloging and Metadata        Primo: MT NA01
O'Shaughnessy-Frey Library
University of St. Thomas

  "Experience is by industry achieved // And perfected by
the swift course of time"--Shakespeare, "Two Gentlemen of
Verona," Act I, Scene iii

From: Program for Cooperative Cataloging <[log in to unmask]> On Behalf Of Yang Wang
Sent: Friday, July 19, 2019 12:19 PM
To: [log in to unmask]
Subject: [External] [PCCLIST] Ending mark of punctuation in 830

Per  LC-PCC PS for (RDA), a right parenthesis ")" is an ending mark of punctuation. So, in the following example in OCLC's Support & Training-Bib Formats and Standards (<>),

[cid:[log in to unmask]]

the final punctuation (period) seems to be unnessary. But in OCLC's bib file, it is not uncommon to see 830 fields end like that. Is it an old practice?