Hello ale, The short answer is that you don’t need a certificate, just print Van Ham’s description of the lot and keep it with the print.
1 - Van Ham is a reputable auction house. 2 - In the auction description there is a reference to the number in the catalogue raisonné, where you can check if the properties are right: Literatur: - Michler, Ralf und Löspinger Lutz (Hrsg.): Salvador Dali - Das druckgraphische Werk 1924-1980, OEuvrekatalog der Radierungen und Mixed-Media-Graphiken, München 1994, WVZ.-Nr. 142b
I don't think you need to check with the catalogue raisonné in this instance, but I have been looking for an opportunity to give a little warning: When an auction house makes reference to a catalogue raisonné it doesn't mean that they have actually consulted that catalogue - they just know from other sales that it is in there, with that particular entry number.
And sometimes the reference is wrong - just copied from another sale without checking the validity of the information.
And sometimes the reference is correct - but the artwork (print) at hand does not fit the description.
Mistakes and wrong assumptions are made, even by the big and reputable auction houses.
____________________ I recommend the Art forum at BidtoArt.com