What is this rootstock

[Gpag]

Hi,
The tree in the photo is a Higan Cherry that is dying. The Higan was grafted onto a rootstock. I have no idea how this was done but am assuming that the trunk is the rootstock and the branches coming off it are the Higan.
I am going to have it taken down but want to preserve the trunk for woodturning and other uses.
Does anyone have any idea what the trunk (rootstock) might be? Knowing that would help me know if the wood is worth saving.
Thanks

 

[Oliver Buckle]

The rootstock is probably Mazzard, a very old cherry, but I can see no junction with the scion, could be grafted at ground level. I don't think it will make much difference to the wood, it will still be cherry either way. The horizontal stripes on the bark are a giveaway for cherry on the whole.