RAMASWAMI, J.

The assessees are manufacturers and dealers in service station equipments such as air compressors, car washers, hydraulic lifts, etc. For the assessment year 1964-65, they reported a total and taxable turnover of Rs. 30, 73, 594.69 and Rs. 9, 42, 804.38, respectively. The assessing officer determined the total and taxable turnover at Rs. 32, 36, 332.19 and Rs. 9, 53, 424.38 respectively. The assessees had used motors and pistons in the manufacture of air compressors and car washers. These motors and pistons were purchased by them issuing form XVII to the sellers and paying the concessional rate of sales tax. The taxable turnover determined by the assessing authority included the sales of air compressors and car washers in which they had used these motors and pistons, which they have purchased after issuing form XVII. With respect to these air compressors and car washers, the assessees claimed that they were not used with electrical energy and that they were inter-changeable with oil-engine and petrol engines and that, therefore, they would not fall under item 41 of the First Schedule and that, therefore, that particular turnover would have to be assessed at