but its the only way to get stamps in 1 piece off the documents.
I am quite keen on cleaning stamps - even very common ones. I don't think leaving dirt, lumps of hinge and gunky adhesive on stamps does anything for preserving them for the future. So most stamps I want to study or put in my albums get a bit of a bath.
I don't suppose "bone adhesive" would do much for the longevity of the stamps either, so cleaning them off would be a good idea. I imagine the glue used would have been like Seccotine that conveniently came in a tube