Peter Paul Rubens lost painting

A few years ago I purchased this same image of Rubens missing painting Judith Beheading Holofernes c. early 17th century Pen and ink and wash with black chalk on paper 15”x20” which is in reverse of this print.  I found some interesting facts about the original painting while preparing it for  exhibition a few months ago at the Meadows Museum Shreveport ,.

According to a letter dated March 18, 1621, the original         ( painting ) belonged to Charles, Prince of Wales. Rubens was not altogether satisfied to be represented in the Prince's collection by so little notable a specimen of his talent, "executed in my youth," as he himself put it. Rubens repeatedly returned to the subject of Judith and Holofernes and  I believe this  could be his earliest image of the theme. Another item of note, is that in  the  ink wash drawing that I own, the Cherubs genitals are draped. I was told by Nancy Bialler at Sotheby’s “ That it could be the work of a student who was learning how to draw by copying this famous and important composition”. Possibly from the original ? I believe  engravers always reversed the composition of the painting .  I understand that Rubens was very specific about how he wanted his paintings represented with the engravers who worked for him. Which begs the question were the cherubs in the original painting draped or undraped? Best regards  Mark Klocko Shreveport , Louisiana