How many backs can be made from one tree ( average).
I have a Chez factory violin I have had since the early 60's. I was told it was built around 1920 - 1930. About ten years ago, I got back into the Violin. I took it to be serviced. The label had fallen out many years ago. The Luither had a violin there for repair with the same back. It had the right label and we studied them together for a long time. They were a match. The Luither did not think it was a big deal. Am I right in thinking they likely came from the same tree?
Small chance, I would guess.
Shamelessly guessing with little foundation I imagine it's possible to get anywhere from 30 to well past 100 backs from a tree. Violin experts sometimes say that violins from the same maker (or city) appear to be from the same log. A pair of violins from the same factory could be from the same log, although how likely it really is would depend on how they sourced and processed their wood. I think a knowledgeable luthier with a good eye can reasonably say whether it's likely two pieces of wood are from the same tree, but you'd have to get into scientific analysis to max out the available level of certainty, and even then Andrew's skepticism retains a seat in the discussion.
a wild guess that it depends on
How many? That would depend on the size of the trunk, the health of the internal wood, and the skills of the luthier. I remember a young string quartet interviewed on the radio many years ago, describing how wealthy donor who liked their playing, but not their instruments, commissioned a luthier to build a quartet from the wood of the same trees (remembering that not all the wood is maple). Two violins, a viola and a cello all from the same trees. I guess quite a few.
I heard somewhere--that most of the top plates of the Guarneri del Gesu violins were made from the same (magic?) tree.
When we visited the maker of one of my violins in Madrid in 1990 (Fernando Solar Gonzales) he told us he had bought an abbey (nunnery) years before to acquire the building's central vertical support in the cellar, made from the spruce main mast of a galleon and that he had used that for the tops of all his violins. Mine, made in 1970 was his violin number 157.
Nunnery wood is good, but not as good as wood from the stairway to heaven. ;-)