Here's a picture of the cams for my "vintage" Viking. It is a machine that was my main machine until recently. It is a Viking 6460 purchased new in 1976. I didn't realize it was "vintage" until I saw it last month in a display of vintage machines in a shop!
The cams are a weak link on this machine as the space where they go can crack and render the machine useless. I have been fortunate to have been very careful with the machine and have it serviced regularly and that part of the machine has remained in tact. I am having problems with the foot pedal overheating and getting parts for this machine is hard since they no longer make them. Love the machine but didn't begin to use all the decorative stitches on it. I have all the cams by one is kept in the machine.