This looks like the correct thread for this question. Is anyone familiar with Den's Collectors Den in Laurel, MD? I'm sure there were other dealers that did sets like this. When did it start? 1976 is the oldest one I have, but I also have a 1979 set done the same way. The PVC pages have his company name and address on them in the same place MVP would put their name. The pages from the '79 set look identical.
I picked this up at an auction about 10 years ago. It is the first I saw anything from that dealer.