CTO, cancelled to order are common on worldwide stamps. For US, it is not uncommon to find precancels or postage dues with gum.
From the SCF Glossary
"Canceled-to-order. Stamps are ""canceled to order,'' usually in full sheets, by many governments. The cancels may be printed on the stamps at the same time that the stamp design is printed. A stamp with a cancel and with full gum is likely a CTO stamp, as CTOs do not see actual postal use. CTO stamps are sold to stamp dealers at large discounts from face value. Most catalogs say whether they price CTO stamps or genuinely used stamps."