No.53 of the typed set of papers also shows that even though Revenue Assistant Mr.P.Sugumaran has been considered along with Junior Assistants Mrs.Jayachithra and V.Ramamoorthy, for promotion to the post of Assistants and it fortifies the contention that all the three posts namely Junior Assistant cum Tupist, Typist, Revenue Assistants have been considered for promotion to the post of Assistants on the basis of G.O Ms.No. 237, Municipal Administration and Water Supply Department dated 26.09.1996. The contention of the learned counsel for the corporation that the petitioner has passed the departmental tests prescribed for the post of Junior Assistants only in December 2007 and that therefore, he could be considered for the post of Junior Assistant-cum-typist only from the said date onwards, cannot be countenanced in view of the fact that orders have been issued even as early as on 02.11.2006 posting the petitioner as Junior Assistant. Even assuming that the petitioner had not opted to work as Junior Assistant and gave his consent to serve as Junior Assistant only in the year 2006, that would not be a proper reason to ignore the case of the petitioner who was working as Bill Collector/Revenue Assistant, which is an interchangeable post. When the post of Junior Assistant cum typist/Bill Collector are interchangeable post and even in the recent order dated 20.10.2010, when the authorities have considered Revenue Assistant for promotion to the post of Assistant, the same yardstick ought to have been applied to the case of the petitioner also, as per the seniority and that the respondents ought to have considered both