It certainly does look like a Newton unit. I reached out to them about disassembly.
I'm guessing the whole cap is threaded on but if it is, my god is it on tight. I'm probably going to try taking a spanner wrench to it to see if I can get any movement. I've looked for any sort of locking ring or pin without luck so far.
They may have stuck some form of loctite on the threads. Perhaps a bit of heat ( heat blower rather than naked flame!) may help loosen it.
