(1) EXEMPT AND EXCLUDABLE INCOME. There shall be exempt from taxation under this subchapter the following:
(a) Retirement systems. All payments received from the U.S. civil service retirement system, the U.S. military employee retirement system, the employee’s retirement system of the city of Milwaukee, Milwaukee County employees’ retirement system, sheriff’s annuity and benefit fund of Milwaukee County, police officer’s annuity and benefit fund of Milwaukee, fire fighter’s annuity and benefit fund of Milwaukee, or the public employee trust fund as successor to the Milwaukee public school teachers’ annuity and retirement fund and to the Wisconsin state teachers retirement system, which are paid on the account of any person who was a member of the paying or predecessor system or fund as of December 31, 1963, or was retired from any of the systems or funds as of December 31, 1963, but such exemption shall not exclude from gross income tax sheltered annuity benefits.