Does this look like a pear root stock?
Are those leaves a little fuzzy (especially on the undersides)?
Yes.
Looks like quince, so it would be a rootstock for compatible varieties of pear or any other quince (though I prefer quince on their own roots).
Why is that?
Because quince are not crazy hard to root like pears, so it doesn’t make much sense to graft them and have to deal with removing rootstock suckers for the life of the tree.
Have you ever grown out quince seedlings? I have a bunch of aromatnya seedlings I started from the fruit from my tree. Some sources say the fruit will be alright and others say it could be bad. I guess they aren’t true to seed. I really started them to use for grafting experiments with loquat.
I haven’t, but it seems that size, shape, productivity and disease resistance are the biggest variables between selections, while fruit flavor has a somewhat narrow range of variation. I’d be surprised if most of them weren’t still very good to eat. In the end, some would probably just end up being more worth their space than others based on the non-flavor based traits.
I wish I had unlimited space to run these kinds of trials. I only have a half acre so I pretty much keep my extra space for trialing the avocados and citrus. My two Rincon valley avocado trees set lots of fruit this spring for the first time. Most dropped but there are still a couple dozen hanging in there at this size: