@ Celtic, You stated :
" I enjoy the different styles/eras of stamps they chose, and one wonders where they found a stockpile of 1-cent stamps from 1934. "

Wall mounted U S stamp machines use to hang in " other " than post offices....

The 1980's and 1990's I would find in convenient stores , Ole U S Stamp machines . Stamps from the 1920's through the 1960's....0.25 cents apiece!!!!
They would come out in a Sanitary cardboard flip, Early Old American stamps....
After every visit there I accumulated Hundreds of these stamps, ALL in Originally packaged cardboard flips.....
I was shocked that More people were Not interested, After showing a fellow employee, He would empty the machines before I did, I eventually bought the machines.....
I too collect Modern Stamp sheets, The music topic has some Awesome stamps, Postal Vehicles from days gone bye Too.....The U S Postal service came out with a Magnet series, The series has colorful magnetic stamp sized magnets of All the stamps in the series, I stopped collecting a couple years ago, Hendrix, Lennon, Military themes..

Very cool to see....

Thanks Commems, Another Awesome topic....