The glue used should be water soluble and I have found the following method best for releasing the kid from the shoulderplate; lay the doll face down on a towel, use wet kitchen roll – a sheet or two folded into a size to cover the shoulders – more than moist but not dripping, lay over the area of kid that needs to release from the bisque especially the edge of the leather, the object here is to allow the moisture to work through the leather and then to soften the glue, it will take some time so check after a half hour or so. You may have to add more water to the kitchen roll as it dries out over time, you need to keep checking back until you can easily peel the edge of the leather from the bisque. Peel as much as comes away easily, you can then place the kitchen roll on the join rather than outside the leather and the glue should soften faster. Work your way gradually until all the leather is released – either enough to see the markings or to remove the head. Obviously if you want to remove the head you will have to do the front as well as the back – same procedure.
When you have finished photographing and copying the markings, or repairing the head or whatever, all you need do is moisten the glue side of the kid again, using damp kitchen roll as before, then with the head in position gently pull the kid back into place over the shoulders. Try to make sure the straps overlap the right way – the glue should make this obvious. Press the kid against the shoulderplate once it is stretched to its original position. Let it dry out whilst keeping it close against the shoulderplate – the glue should set it back so that you should not be able to see that it has ever been removed.
I hope this has helped – please contact me if you need more information or advice.