B.N. SRIKRISHNA, J. :---These are two writ petitions under Article 226 of the Constituion of India filed by the Employer and the Workmen, respectively, challenging the Award of the National Industrial Tribunal dated 8th April, 1991, made in Reference No. NTP-2 of 1987. Since the two writ petitions are in the nature of cross-petitions, the parties shall, hereinafter, be referred to as they are arrayed in Writ Petition No. 2416 of 1991, in which the petitioner is the Employer, Respondent No. 1 is the Presiding Officer, National Industrial Tribunal, Bombay and respondents 2 to 8 are Trade Unions/Associations representing the present and past workmen of the petitioner-Employer.

2. A Company known as ICI (India) Private Limited was incorporated some time in 1926. Between 1939 to 1961, three Indian subsidiaries, by name, (1) Alkali and Chemicals Corporation of India Limited, (2) Indian Explosives Limited and (3) Chemicals and Fibres of India Limited, of the parent U.K. Company were set up in India. In 1982, the other subsidiary Companies were amalgamated with Indian Explosives Limited. In 1989, the name of Indian Explosives Limited was changed to ICI India Limited which is the name of the petitioner as shown in the petition. The petitioners has several manufacturing factories at different places in the country. The locations and details of products manufactured in such factories are as under :

1. Panki (Up) .... Fertilizers, Catalysts

2. Gomia (Bihar) .... Explosives

3. Rishra (W. Bengal) .... Paints, Rubber Chemicals

4. Hyderabad (A.P.) .... Paints

5. Thane (Maharashtra) .... Polyster Fibre, Speciality Chemicals

6. Ennore (Tamilnadu) .... Pharmaceuticals, Agro-Chemicals

7. Bangalore (Karnataka) .... Seeds

3. The petitioner employs about 8,500 employees in its establishments all over India. Out of these 8,500 employees, it has categorised about 517 as Management Staff required to perform Managerial and Administrative functions. The rest are categorised as Non-Management Staff and comprise "workmen" within the meaning of section 2(s) of the Industiral Disputes Act and also Supervisory Staff who are not "workmen".

4. The Non-Management Staff of the petitioner had always enjoyed the benefits of gratuity and contributory Provident Fund which were more liberal than those provided for in the respective applicable statutes. In addition thereto, the petitioner had been giving, on ex-gratia basis, a monthly pension to the retired employees and widows in a few cases of hardship. In 1962, the petitioner announced a Pension Scheme as a third retirement benefit which was brought into force from 1st January, 1961. Since then the Scheme has been revised from time to time by the petitioner, though ad-hoc. There is dispute between the parties as to whether the Scheme of Pension introduced initially was the result of a settlement in an industrial dispute, or voluntary. The Scheme was revised with effect from 1-1-1966, 1-4-1975 and 1-10-1977. These revisions were made applicable to the existing pensioners also. Though ad-hoc, the revised pensionary benefits were made applicable to the existing pensioners, the erstwhile pensioners as well as to those who retired after the aforesaid dates. However, the revision made with effect from 1-7-1976 was made applicable only to those workmen who retired after that date. There was a further revision made with effect from 1-12-1979 which was made applicable only to those who retired on or after 1-7-1979. The revisions made with effect from 1-6-1980 and 1-7-1984 were made applicable only to those workmen who retired prior to 1-12-1979. A further revision was made with effect from 1-4-1985 classifying the pensioners into three classes, (a) those who retired prior to 1-10-1977, (b) those who retired between 1-12-1979 and 31st March, 1985 and (c) those who retired after 1-4-1985. The different classes of pensioners were granted different benefits by way of revision of pension as the applicable pension formul