Hi Hilfe, welcome to Outdoorking.

From the little information on this model I can find, it does indeed seem to be a Cox with Victa badges. I suggest you do two things:
1. Contact Cox - the easiest way would be to use their "Contact Us" form on-line:
http://www.coxmowers.com.au/?page_id=826

2. Ask them for the Cox model number for your mower, and if possible for the owner manual and Illustrated Parts List for their version.

3. Tell us what you find out, so the next person who needs to know will be able to find the answers in our archive.

I think this will solve just about all your problems with service information, and with sourcing replacement parts.