Examples from the Web for imperforate
It was stipulated that applications for these imperforate stamps should be made to the Postmaster at Ottawa.
The 1c in coil form was also issued with the 12 perforation at top and bottom and imperforate at the sides.
The shell is thick, imperforate (no umbilicus), and usually has flat, spiral ribs.The Sea-beach at Ebb-tide|Augusta Foote Arnold
The first stamps were imperforate, necessitating the use of scissors or other instrument in separating them.What Philately Teaches|John N. Luff
The inverse ratio of seven to one for a catalog value would make the perforated stamp list $42 with the imperforate at $6.Canada: Its Postage Stamps and Postal Stationery|Clifton Armstrong Howes