An imperforate or imperf stamp is one without perforations or cut separations of any kind around a stamp or stamps in a sheet. The best known and most widely collected of these in the U.S. are the 1930's stamps that resulted from Farley's Follies, the scandal of U.S. Postmaster General James Farley giving special printings of stamps to friends, dignitaries and political cronies. When Farley's actions were discovered the stamp collecting community demanded their own special stamps, which they got.
The Baseball All-Stars press sheets that the USPS is making available to the general public brings to mind the Farleys. Like those sheets, the baseball press sheets are being issued in uncut (as they come off the press and before the larger sheet is cut into the familiar stamps sheets we buy), including imperf versions of these (stamps not cut between each other on the sheet). These latter sheets will be printed in smaller quantities than the original stamp sheets.
And as in the earlier situation, some collectors are crying foul over the baseball sheets. While there will be position varieties available (cross gutter blocks, taken from the center of the sheet and showing stamps from both sides (left and right), etc.) these will be so scarce that the average collector will never be able to add them to their collections. This is similar to what stuck in collectors' collective craw when PMG Farley got caught printing instant rarities. Although the Baseball All-Stars situation is different in certain respects, it seems like the USPS has sparked some controversy with the new sheets. Be sure to check back here as the story is still developing.
Stamp Image © USPS