Sh.Gautam Godhwani Ji,
This is an extract from legal dictionary based on Supreme Court judgements. It may be useful.
Source : A book titled, " Supreme Court Words & phrases (Third Edition) compiled by Surendra Malik and Sumeet Malik published by Eastern Book Company at page 1311"
"The word, ''part'' means an appreciable amount and not an insignificant one. The 'part' in other words, must be substantial part. What is substantial would depend upon the facts and circumstances of each case. MCD Vs. Children Book Trust 1992 (4) TMI 237 - SUPREME COURT Date of decision : 21.4.1992"
More comprehensive meaning, essence and message have been given at page 1311 in the above dictionary. Worth perusal. It is an absolutely must to arrive at correct classification of the goods.