Yet another liner question

Our 1893 house was thoroughly renovated circa 2006 before we bought it. There is a centrally placed open fireplace with a masonry chimney with one 8" metal liner which runs up to the cap. A second metal pipe runs parallel from the gas boiler and water heater in the basement.
What can I assume about this install regarding code for that time, specifically whether the liner is insulated or not?
I've been using a smallish insert with a 6" to 8" adapter plate for the past few years but have been planning to upsize to freestanding and want to be safe on the chimney side of things.

It would be hard to tell if the liner is insulated. It would only be required if the clay liner (if it had one) was busted. If it has no clay, then it should be insulated. You might be able to pull the top plate to inspect. Be careful, the top plate and clamp might be holding the whole thing up.