[john70t]

https://www.sciencenews.org/blog/gory-details/leonardo-da-vinci-may-have-invented-3-d-image-%E2%80%98mona-lisa%E2%80%99
It appears that the two paintings may have been painted at the same time, in the same place, both artists tweaking the work in the same ways.

If true, differences in the two paintings indicate the Prado version was probably painted by a student, a practice fairly common in Leonardo’s studio.