I have processed (includes making thumbnails for each one) and uploaded the half million
PSE images and the PSE certification database feature is now done! Whew, that was a grunt.
I have also integrated the PSE certification data into the other existing Stamp Smarter US stamp databases. In other words, you can now quickly lookup any US stamp and have the following standard information at your fingertips;
Catalog Number, Description, Denomination, Color, Details, Perforation, Printing Type, Gum Type, Paper Type, Number Issued, Printer, Date Issued, Watermark. But additionally you also have one click access to; Plate Numbers, Tagging Info, PSE Certifications, and eBay
I do not think that you can find any singe resource (online or hard copy) which has this much detail for every US stamp. And it is free!