Not possible to tell from such pictures.
Only when you power up the monitor with a known familiar image and look at it closely, then you will know for sure.

IME, Hitachi always uses shadow mask.
Not only that, but the tube inside their monitors should be their own. They were among one of the few tube manufacturers... and IMO the best. I have a Superscan 814 (21" screen) and it has a beautiful picture, despite not having a glass front.
Hitachi's are also built very well too - all or mostly high quality Japanese caps on their board (at least my 814 was that way.)

Let us know what you find with yours, though.