Hello Chris,
The HC908 devices that have a trimmable internal oscillator are limited to a few series only - Qx series, EY, GT, but not many others come to mind. A few other series do have an internal oscillator, but is not accurate or stable with voltage and temperature.
Trimmable internal oscillators seem much more prevalent within the various 9S08 series, which are more recent devices.
Regards,
Mac