All of the OS I ever purchased were from the same drug store in Linton. Indiana. The only place anywhere close to us {about 15 miles away). Series 1 through series 15.
One store for all 15! wow
My small town of Albemarle, NC was a hodge podge of stores and only a few series at each, and I don't recall seeing one single series at multiple locations.
1st series cloth, 5th series: Eckerds Drug
2nd, 8th: Medical Pharmacy (complete with food counter w/stool seats)
3rd: downtown newsstand/magazine store
4th: family owned produce store
6th, 11th: McLellans five and dime
10th: Hooters fishing supply across from the ymca
Never saw 1st, 7th, 9th, or 12th and above.
My last purchase was the one and only box I ever bought--it was at McLellans. It was 11th series(I found out in 1999), but had (I also found out in 1999) 2nd series UK checklists! The checklist titles did not completely match the stickers, and of course the "2nd series" title was confusing. I kick myself for not saving anything but the stickers. I had to open the box in secret (down the street in the upstairs storeroom of my uncle's music store) because my parents hated me buying wackys.