Classification of goods which are potentially within the scope both of heading 90.27 and of heading 70.17 (laboratory glassware).In these cases, classification is governed by the following considerations :
(1) If an article has the essential character of glassware (whether or not graduated or calibrated, and whether or not with subsidiary stoppers, connections, etc., of rubber, etc.), it is not to be classified in 90.27 even if it is normally known as a particular instrument or apparatus.
(2 ) In general, instruments normally cease to have the essential character of glassware when they consist partly of glass but are mainly of other materials, or if they consist of glass parts incorporated or permanently fixed in frames, mounts, cases or the like.
(3) The combination of glass parts with measuring instruments (e.g., pressure gauges, thermometers) may, in practice, provide grounds for considering such instruments as proper to this heading.