I guess the Israel postal service recognized in 1957 that collectors were only interested in tab stamps. As a result, I guess, they printed some sheets that had only the tab stamps. I know of 5 such sheets printed, all in 1957. The one here on the left has the top row of partial stamps imperforate, while the one on the right has the top row perforated. You can tell they are not just cut down regular issue sheets by the serial number. On the perforated sheet, only the bottom portion of the serial number is visible on the center stamp, while the imperf sheet has the whole number clearly visible. I guess there must have been collector backlash or something, since these sheets were only done 9at least as far as I know) for 3 issues of 1957.