Sorry to hear of his illness. I assume the vet is avian certified or the equivalent; this is a tricky diagnosis. Has the vet discussed techniques to remove the metal?
That's a very good and important question Scott, I'm hoping that the Vet went over the entire process with them, because depending on what it is and how large it is determines the type and length of treatment for this...Sometimes it's very easy, sometimes it's a long course of chelation-therapy, where they actually have the metal bind to a substance they inject into them, so that the body can then safely excrete the injectible substance normally, with the metal bound to it, preventing it from being absorbed by the body...I haven't seen this done in quite a while, but they used to inject Calcium EDTA as the binding-agent...I don't know if they still use it or if they use something else...I hope their vet is certainly a CAV and is experienced in doing this, and has explained the entire process to them..
The other thing that needs to be addressed is that the metal that he ingested could very likely have been ingested in your home and not in the prior-owner's home, it just depends on what kind of metal it is. Some metals have to build-up in the body over-time to cause outward signs and symptoms of illness and to cause physiological responses, such as an enlarged-liver, and then some metals cause extremely acute-illness and physiological responses (acute metal toxicity)...So I'm hoping that the CAV can go over this with you and determine exactly what type of metal it is, as well as how much is inside him, because if it was something that he got hold of in your home during the past week that you've had him, you definitely need to do a search around the places in your home he can get to, things he can get a hold of or has been chewing on, etc. If it's just tiny little flecks of metal inside him, then that is typically the kind of metal poisoning that takes time to develop, and is usually from them chewing on something over-time, such as the coating on their cage-bars, or some kind of metal or ceramic object, painted objects, etc. They are such little buggers when they are young, well, all the time really, lol...they can chew on anything and everything they can get a hold of...
