"What was used for the extraction, the MCT oil? Or was there a different process used to extract and then MCT oil added?"
That tincture was made via a method called ‘supercritical CO2 extraction’, which is easily the most preferred and safe method of extraction. CO2 (carbon dioxide) is the inert gas we all exhale during each breath. In order to extract each cannabinoid, CO2 is manipulated by applying specific pressure and temperature points, individualized for each cannabinoid.
Though less common today, butane and other petroleum-based solvents were utilized via a similar process. However, petroleum is not inert, which leads to a much more dirty and harmful end-product. Furthermore, most petroleum-based extracted end-products possess the odor and taste of butane. And in contrast to those products created via CO2 extraction, petroleum-based extracted products are known to cause respiratory problems when vaporized. So, make sure that all of the cannabis products you consume — such as vaporizer cartridges, edibles, sprays, oils and tinctures — were produced via CO2 extraction.
I hope this helps!