Opel Candybar mobile phone - Am I out of luck?

Hi experts,

I'm checking out a mobile phone for a solicitor, attempting to retrieve deleted text messages if possible for their client.

I did some research before receiving the phone, being told it was Opel brand it looked like they used a custom Android designed for accessibility.

But on retrieving the phone - an Opel CandyBar - it does not look like its an Android device!

Looks like this (Model: CandyBar OMCB19B)

I had a poke with a couple of tools including `adb`, put a Metasploit apk on an SD card but it didn't offer to open it so I'd call that conclusive!

However using Disk Utility on the Mac I could kind of image the phone - all 342k of it apparently. This is obviously not right, since there's at least 76 SMS messages on there, and the SMS settings reckons that storage is at 69%..

Previously, this very same client had an antique Nokia that I took to a forensic accounting place that uses Cellebrite, and of course nothing useful was on it. 

So I guess two questions:-

1) Does anyone know anything about these phones; and

2) Am I likely to be able to get deleted messages off this type of custom-OS phone in any case, even with something like Cellebrite?

Thanks in advance for any help.. 😅