§ 431. Salary base for computing retirement benefits. In any
retirement or pension plan to which the state or municipality thereof
contributes, the salary base for the computation of retirement benefits
shall in no event include any of the following earned or received, on or
after April first, nineteen hundred seventy-two:

1. lump sum payments for deferred compensation, sick leave,
accumulated vacation or other credits for time not worked,

2. any form of termination pay,

3. any additional compensation paid in anticipation of retirement, or

4. that portion of compensation earned during any twelve months
included in such salary base period which exceeds that of the preceding
twelve months by more than twenty per centum.