Old "Do Not Disturb Signs "pop up at paper shows from time to time and I often buy them . Here are a few of the older ones. Marilynn Gelfman Karp wrote an excellent book called
In Flagrante Collecto in which she devotes a few pages to these signs.It's one of those delightful books that is hard to not read and smile since it covers an amazing range of oddball collections.
While I am recommending books let me mention The Big Short by Michael Lewis.
Be warned this one will not bring a smile to your face. If you have contempt for politicians and financial experts or just want to get a clearer understanding of the housing crisis and the financial mess we and our grandchildren are paying for, this is one you ought to read.