It’s another under license production by Hiradas Technika.
Do you use the module port to expand memory ? Yes ! 16KB more with CE-161
But they don’t !
Their PTA-4000+16 is nothing but a PC-1500 with a self made 16KB memory board inside.
Crazy, no ?
Stupid ! The module port has being removed and it’s door is glued.

Look at the buzzer… it’s now on the CPU side.