Mods please forgive me if this has been asked but I didn't know how to word it. Couldn't find it in the Scott intro to the section, but is a stamped envelope with a preprinted return address considered used or Unused? I have to discern between U390, 391, and 392 which have some catalog value (around 20$) so they're definitely not postage, but are they worth a lot less since they have the return address? None have been used.
I have know idea but if it has not went threw the postal system then it is unused. Let's see what other more learned members have to say. I am interested myself what they have to say. Good question I am glad you asked.
Unused, printed address priced as mint but with a discount for the address. Typically halfway between mint and used values when used is less than mint. Unfortunately, for many items used is more scarce than mint which makes a simple pricing formula nonexistent.
oldboldandbrash, Preprinted return address is considered mint. But it does affect value some, as many collectors of mint entires prefer nothing but indicia on the entire. However, some varieties only come with a preprinted return address.
Preprinted address does affect value significantly as pointed out by eyeonwall.