When opening some multipage tiff images with unrecognized tags, graphicsMagick is unable to open them. I get the following error
gm display: Internal error, unknown tag 0xc697. (TIFFFieldWithTag).
I also get the same error with 'gm identify'. I can open the image with ImageJ no problem, and ImageMagick opens and recognizes all frames (although it also gives an warning about an unrecognized tag).
I attached a file that should be able to duplicate this error. I'm using GraphicsMagick 1.3.5 2009-01-26 Q8 in linux.