I noticed that when Joe Biden was signing the stack of executive orders yesterday he used a new pen for each one which was than placed with the executive order. What is the reason for this? The only thing I can think of is that the pen is stored separately and, in case of doubt about the authenticity of the order, the ink in the pen and on the order can be matched.
//However, the document may also be, for example, an executive order, ... The pens were then given to attending dignitaries and supporters of the bill//
When we do an eye testing session for dogs at present we have to provide a new pen for each owner to complete their forms (unless they bring their own) and they are then told to keep the pen to avoid contamination from them to the next person.
I think most shops are 'stationary', Spicerack ;-)
Your post reminds me of a label on a filing cabinet at the school I taught at, which read "P.E. Stationary". I've heard of changes to the curriculum but that, surely, is taking things a bit too far!