Judgment

DWIVEDI, J.:- All these appeals raise a common question of law and are being disposed of by a common judgment.

2. The employees of the Mysore State Road Transport Corporation are divisible into three classes: (1) the employees of the erstwhile Road Transport Department of the State of Mysore (hereinafter called the Mysore employees) (2) the employees of the Bombay Road Transport Corporation who were working within such districts of the State of Bombay as were integrated with the State of Mysore (hereinafter called the Bombay employees), and (3) the employees of the Road Transport Department of Hyderabad working in such areas as were integrated with the State of Mysore (hereinafter called the Hyderabad employees). The employer and the employees concluded an agreement on January 10, 1958 in respect of certain terms and conditions of service. The agreement was made operative from April 1, 1957. Clause 5 of the agreement dealt with the dearness allowance payable to the employees. The dearness allowance was fixed on a graduated scale. It appears that the Bombay and Hyderabad employees were getting a higher dearness allowance which was an accident of the reorganisation of States. Accordingly proviso (a) to cl. 5 provided that they would be entitled to continue to draw dearness allowance at the rates which were applicable to them on November 1, 1956 and January 1, 1957 respectively. The agreement was to remain effective till March 31, 1960. On February 10, 1962 there was another agreement between the two parties. It was made effective from April 4, 1960 and was to continue until March 31 1965. Clause 4 dealt with dearness allowance. The allowance was increased by Rs. 5/- in respect of all the employees except those who were getting pay between Rs. 301 and Rs. 500 per month. Proviso (a) to cl. 4 was similar to proviso (a) to cl. 5. of the earlier agreement. A third agreement was concluded on March 20, 1965. This agreement came into force on April 1, 1965. Clause 15 provided for dearness allowance payable from January 1, 1965. The marginal note to cl. 16 (1) is revision of pay scales . The parties construed the first part of this clause differently and hence the litigation culminating in these appeals. The text of the clause will be set out later after we have noticed certain orders issued by the employer between 1960 and 1964.

3. The first order was issued on March 22, 1960. This order fixed the rate of dearness allowance of the employees with effect from January 1, 1960. Broadly speaking, it increased the dearness allowance of the Mysore employees by Rs. 5/-. There was another increase of Rs. 5/- in dearness allowance with effect from January 1, 1961. The order increasing the amount stated that the increased dearness allowance would be payable to the Mysore employees as well as to the Bombay and Hyderabad employees provided they opted for the Mysore rates of dearness allowance. There was a further increase of Rs. 5/- in dearness allowance with effect from April 1, 1963. But the Bombay and Hyderabad employees could avail this addition only if they opted for the Mysore rates of dearness allowance. The last increase in the dearness allowance was given with effect from April I, l964. The amount of dearness allowance was increased by Rs. 5/-. The Bombay and Hyderabad employees could avail this increase only on their opting for the Mysore rates of dearness allowance. An interim relief of Rs. 5/- per month was also granted to the employees with effect from April 1, 1964. This interim relief was not subject to option. Consequently, the Bombay and Hyderabad employees also were benefited by it.

4. Clause 16 (1) of the agreement of March 20, l965 relevantly reads:

"The pay-scales of the Corporation employees not having been revised since the first Truce Agreement of 10-1-1958, the employees have been given interim relief as well as increased Dearness Allowance benefits as follows:

Date Amount

Dearness Allowance 1-1-1960 Rs. 5/- p.m. (minimu