I score the finish where the back and sides come together first, with an exacto knife. Then I try to work the exato knife further into joint. I also take hot water and apply it to the joint while I work in a heated spatula. The combination of moisture and heat will quickly separate a hide glue joint, if that is what it was glued with.
Hate to take this thing apart, It turned out beautiful with the French polish finish. But neck wasn't solid at all without the button on the head of the backside. Should stil look good when I'm finished, I hope!
Sharply tap along the edge of back plate with your knuckle and listen for a "loose" sound. If you ever done this with a guitar top looking for a loose brace you know the sound. That's where you insert your spatula (I use a painter's pallet knife that I cut down to about the size of my thumb). An 80-100 yr. old violin probably has a couple of open spots, if not lay a hardwood block against the lip of the back edge and tap it to open the seam. Hide glue is very strong, but brittle, and will give. Once you have the tool inserted, work the edge agains the glue seam, being careful not to dive into the rib or back. It's like cutting an apple with a paring knife.
The process goes really quickly, I wish removing a guitar back was to simple.
I'm not familiar with the term "nose"...is that another name for the button?
I found the term for the "button' or 'nose' while researching reconstruction of the violin. The part I am referring to is the part of the back the heel of the neck should be attached to. Thanks for your help!
I plan to construct a 'button' from a small plate of maple that will be glued inside the back 1 1/2 - 2" long apx 1 1/2" wide which will hang out and down even with the back and attach to the heel of the neck to support the the neck. A bit of carving.