The question is do you have a gaslight with which to expose it?
Simon ILFORD Photo / HARMAN technology Limited :
Bit of a spooky co-incidence this as I have today been looking at original paper labels of several dozen paper types that have been found in a store cupboard in our marketing department that were removed from the old RAJAR Photo works at the top of the Mobberley site. I have a virtually identical label in mint condition ( never seen the light of day for decades ) except it says Gaslight Postcards.
I am going to have them all scanned and put on the website, the old Rajar ones are very interesting including Rajina brand.....and one I had not heard before ILFORD Valora paper.