SG29 - marginal block showing ribbing

Vertical ribbing can be seen on the right-hand margin.

Ribbing was suppose to be caused by the serrated clamps that held the paper in place around the margins during printing. The paper was also slightly damp which causes so many of these stamps being mis-perfed as the paper stretched and of course took on this ribbing effect.

It should also be noted that the watermark around the margin includes 5 lines around the complete border except for the word POSTAGE at the top and bottom and twice on each side of the plate. (source Postage Stamps of Great Britain Part 1). However the ribbing seen here consists of 4 vertical lines and is not present at the top of the plate, see example

The corner letters of the two right-hand stamps are HJ and IJ, (column 10)
they should be HL and IL (column 12)!

It could be a forgery; or most likely, the right-hand margin has been very cleverly fixed to the rest of the block (but note that the marginal inscription is correct for rows H and I) or it could be a very rare item indeed. On closer inspection it turns out that the printing has been damaged by the perfs but is HL & IL

Scan courtesy Elstree Stamps

Main Stamps page