He signed his work with a monogram which had been read by the 19th century city archivist of Leuven Edward van Even as representing the letters IVR.
Based on this and other evidence it became possible to identify the monogrammist IANR with Jan Rombouts the Elder who was referred to in contemporary records as a painter.
[2] Jan Rombouts is regarded as an important modernizer through his complex compositions, moving figures, lively and colourful palette, meticulous eye for detail and pseudo-Renaissance architectural elements.
[7] At the same time Rombouts did not stray too far from the traditions of Early Netherlandisch painting as exemplified in the work of his famous fellow townsman Dieric Bouts.
[2] His oeuvre is now believed to comprise a handful of paintings (comprising five double-sided altarpiece wings and a single panel), seven engravings, a drawing on wood panel of The Judgment of Solomon, a vidimus drawing for a four-light church window (Amsterdam, Rijksmuseum) and more than two dozen painted glass windows, some of them believed to be after Rombouts’ design rather than by the master himself.
The result is a work rooted in the 15th century Flemish tradition of Early Netherlandish painting but with a focus on Italy and the mannerism of among others Bernard van Orley.
His principal panel works are the monogrammed wings of a dismembered altarpiece depicting scenes from the New Testament stories of the Conversion of Saint Paul and The Fall of Simon the Magus (M – Museum Leuven) which are monumental and in a classicizing style.
The stained glasses from the former Carthusian monastery in Leuven (parts of which are now in New York's Metropolitan Museum and the Riverside Church) have been attributed to Rombouts and his workshop.