On 13 December 2018, the source wrote:

SPECIAL NOTICE

In January 2019, the Board will discontinue publication of data on the outstanding amount of U.S. dollar-denominated traveler's checks of nonbank issuers. Dollar-denominated traveler's checks serve as an alternative to demand deposits and currency as a means of payment and therefore are included in M1. Nonbank traveler's checks have fallen steadily for many years to a point at which they represent an immaterial share of the monetary aggregates. The insignificant amounts no longer justify the burden of collection and publication of these data.

The date of the last reported value in the "Traveler's checks" column in tables 3 and 5 of the H.6 statistical release will be December 31, 2018. 

Properties:

• The weekly series run from 6 January 1975 to 31 December 2018.
• The monthly series run from January 1959 to December 2018.

In response, we have:

1. Marked the series metadata as discontinued.
2. Marked the catalog entries. (These columns still exist in the reported tables, and will presumably continue to do so until the December 2018 period "scrolls off the top".)

The series reside in the historical catalog:

• United States » Financial » Money supply » H.6 - Money Stock and Debt Measures

and are:

• TRAVELW.IUSA
• XTRAVELW.IUSA
• TRAVELM.IUSA
• XTRAVELM.IUSA

References

• Money stock and debt measures - H.6 release - Current release
• Announcements