Frits Lugt’s great work Les Marques de Collections de Dessins & d’Estampes is now online, courtesy of Lugt’s Fondation Custodia. HERE is the link and just below is a screenshot of the search fields.
The first volume was published in 1921, a supplement printed in 1956, and the 2010 supplement is just now available online (from what I can tell, there won’t be a paper edition). All three are online and together they add up to being an invaluable database. I immediately bookmarked the site and set it as a start page on my phone. The search fields are easy to understand, navigate, and reset. For the name and place fields, you can start typing and without completing the word, a selection of names or places materializes. Many of the mark entries reproduce just the line drawings from the earlier Lugt volumes. Especially useful are the entries that have both the published reproduction and a photograph. In time, maybe all of the reproduced marks will be supplemented by photographs.
After a quick look through, one can see that there are still many marks needing to be identified. If enough people use it, especially museum people with their vast holdings, and they share their findings, more and more marks will be identified. Since it is so easy and fun to use, the database will surely grow. It is also free, wonderfully free.