N.Y.C. Charter § 275: Section 275. Investment of sinking fund moneys.

The comptroller may invest the moneys of the several sinking funds of the city established prior to July first, nineteen hundred eighty-one in any of the following securities:

1. Obligations of the city of New York.

2. Obligations of the state of New York.

3. Obligations of the United States or of any agency, subdivision, department, division or instrumentality thereof, or obligations fully guaranteed or insured as to interest and principal by any agency, subdivision, department, division or instrumentality of the United States, acting pursuant to a grant of authority from the congress of the United States.

4. Obligations of the municipal assistance corporation for the city of New York.