Preferred stocks of closed end funds (CEFs) tend to be some of the safest preferred stock in existence. This is because of the requirements that the CEF have at least 200% asset coverage of “senior securities” which means debt and preferred stocks.
As you can see in the chart below virtually all of the issues are solidly investment grade.
It is CAUTIONED that all but 2 of these issues are perpetual preferreds meaning they are sensitive to interest rate movements.
In this case safety of the security doesn’t mean safety of the share price. While the shares are extremely safe the share PRICE can be decimated if interest rates move strongly higher.