(2)For every completed year of service or part thereof in excess of six months, the employer shall pay gratuity to an employee at the rate of fifteen days' wages based on the rate of wages last drawn by the employee concerned:Provided that in the case of a piece-rated employee, daily wages shall be computed on the average of the total wages received by him for a period of three months immediately preceding the termination of his employment, and, for this purpose, the wages paid for any overtime work shall not be taken into account:Provided further that in the case of [an employee who is employed in a seasonal establishment and who is not so employed throughout the year] [ Substituted by Act 25 of 1984, Section 3, for " an employee employed in a seasonal establishment" (w.e.f. 1.7.1984).], the employer shall pay the gratuity at the rate of seven days' wages for each season.[ Explanation .-In the case of a monthly rated employee, the fifteen days' wages shall be calculated by dividing the monthly rate of wages last drawn by him by twenty-six and multiplying the quotient by fifteen.] [ Inserted by Act 22 of 1987, Section 4 (w.e.f. 1.2.1991).]