My guess and of course only a guess. The 1921 was mostly used because it has the highest mintage in Peace and Morgan dollar designs. So back when stickers were being used these would have been the most common picked up by the bag at the local banks.

The stickers are in really good shape on your dollars. Especially the Hacienda which are very very thin clear stickers. So many sticker dollars have big damage to the stickers so to have nice readable ones is a big plus.

Thanks for sharing.

Dennis