I currently work as a consultant to Bonhams UK and USA for advice on the drawings that come to them for valuation. I also offer this service to other clients and you might be interested in reading Reasons to be cheerful, an article I wrote on drawings sold in the UK auctions, that appeared in Gavel magazine.
Please do contact me on crispian@riley-smith.com or my mobile +44 7771 552509.
Friedrich Brentel (Lauingen circa 1580-1651 Strasbourg)
The Crucifixion