Attribution is one of the most important facts of any painting in a museum or gallery, even more than its date, subject matter, or material. If a work can be said to be definitely the work of a particular artist, that fact can change the course of art history, solidify or alter the art world's view of a painter - or undermine a famous painting's apparently lofty lineage.

The new effort by Glasgow Museums, aided by colleagues at the University of Glasgow and the Prado in Madrid, to find out more about Lady in a Fur Wrap, attributed to El Greco, is partially driven by the importance of such a clear attribution, but also by curiosity. Who was the lady? For a time, it was believed to be El Greco's daughter: until it was found that the great Spanish-based Cretan painter had no daughter. And, Glasgow museum experts believe, there is a possibly unsolvable 'conundrum' in the work. Direct but informal portraits of 'Early Modern' women such as this are extremely rare, and this painting was probably unique in its Spanish context.

The painting has already been studied meticulously by experts at the Prado in 2014. So this new investigation centres on five other works, which could provide key points of reference by which to judge the Lady. There will be new lines of inquiry, including garments and jewellery, and the input of leading scholars of Spanish art, dress and other fields will be brought into the study.

Advanced analytical techniques, including Gas Chromatography Mass Spectrometry - a procedure for providing detailed chemical information on the organic materials found in paint samples, especially binding media - will also be utilised.

Pippa Stephenson, curator of European Art at Glasgow Museums, admits the new investigation may not solve the mystery of the painting conclusively. Its enduring riddle may, indeed, provide some of the famous painting's mysterious power.