Hello Pavdoum, and welcome to the ODK forum.
I think i have one out there somewhere, i'll have a look tomorrow and post some pics for you, if i can find it.
Feel free to post some pictures of your machine if you like, as it is a fairly rare model. A Mustang 20 (aka 505)with SP and keystart weren't exactly the run of the mill everyday choice for most mower users.
Instructions on how to post pics can be found here
HERE