(1) Certain other instruments which may have investment characteristics are approved for state-chartered banks. They are the following:

(a) banks may invest up to 100% of their capital and surplus, per accepting bank, in bankers acceptances;

(b) banks may invest, on a per issuer basis, in certificates of deposit (CDs) or deposit notes from insured financial institutions up to the greater of 20% of their unimpaired capital and surplus or the maximum amount of federal deposit insurance available for deposits. This limitation applies to the deposit and any accrued interest;

(c) banks may invest up to 20% of their capital and surplus, per issuer, in commercial paper provided the commercial paper is rated A1 or P1, at the time of purchase, by a recognized national investment rating organization. Equivalent ratings from other established and generally recognized national rating organizations may be substituted;

(d) banks may invest up to 20% of their capital and surplus, per issue, in privately issued CMOs and REMICs;

(e) privately issued CMOs and REMICs will not represent more than 40% of a bank's investment portfolio, or more than 400% of a bank's unimpaired capital and surplus, whichever is the lesser; and

(f) banks may invest up to 20% of their capital and surplus, per issuer, in trust preferred securities. These bonds must be investment grade, i.e., rated in one of the four highest grades by a recognized national investment rating organization. Other rating services may be used if the gradations are equivalent to those above, and the rating services are identified by the bank's investment policy.