I have a German made altimeter (broken) in use as a paperweight whose subscale goes down to 750hPa ! That should be good to about 7000 ft.
Incidentally I once had occasion to file an airprox, which was flying nonradio in a little puddlejumper just-off the West Scottish coast. I listed my altitude at 900 ft QNH. A few weeks later I had a call from the Airprox board, and the conversation went something like this...
"You list your altitude as 900ft QNH"
"That's correct"
"What setting did you have on your altimeter"
"I don't know, I didn't take a note of it".
"Then how do you know it was set to QNH?"
"Because I set it to zero just before taking off from the beach halfway between the low and high tide marks".
<long pause>
"Err, there may be something wrong with that, but I'm not sure - I'll get back to you".
And he never did
G