Vintage Bewator Keypad code change?

I Have a vintage Bewator keypad that controls a magnetic door lock with no operating manual and I want to change the code, can anyone advise on how to? I do have a working 4 digit code.
Is it done via jumpers on the board or can it be done via the keypad?

 

Model number ? You may have to open it up , some of the early ones like that one had a controller

 

There are two separate 6 or 8 digit codes, set via jumpers inside the unit. One set is the master password, then the other a secondary one. Idea was the master was always the same, but restricted to trusted individuals, the secondary one was issued to anyone who might need it, but could be changed often.

There is a socket for a key in the bottom, if that is turned, it releases the entire panels to gain access to the rear of the PCB where the jumpers are set.

 

Thank you Sparkymarka & Harry.
Unfortunately the key has been misplaced/lost to open up the box to get model number etc, so I think I’ll have to drill out the lock to open the box then replace lock.

 

The lock includes a sort of hook which turns, to hook onto a bracket on the front button panel. The top of the panel sits in a sort of groove in the case. I have the same model fitted on my small garage 'people' access door. I got fed up of forgetting the key when going out to my workshop, sort I fitted one of those I had in my bits box. They are not intended for outside, so I made a cover to keep rain off.

 

Thanks Harry your description was spot on with the hook.
I drilled the center barrel out and have successfully changed the code.
Now just need to source another lock barrel.
Thank for all your help.
Picture below of unit

 

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