I was in the midst of sorting a collection and came across this stamp. A Mint, never hinged copy of C58.


The Hindenburg issue of 1936, like the OSTROPA sheet of 1935, contained Sulfuric acid in the gum. Those stamps that do not have the gum soaked off eventually turn black and brittle. Eventually, these stamps will crumble. The corner on this example broke when I removed it from the mount. Sadly, it is too late to soak the gum off this stamp; the damage is already done.
This set and the OSTROPA sheet are valued without gum. When the time comes to add these to your collection, be sure you have a look at the backs lest you buy an original gum space filler.
Brian