I have an Ambassador that's a slightly different model than yours. Mine was made by Toyota.
It's cast into the bottom of the base. Your machine might or might not be.
I think the Japanese just kept modifying the model 15 clones until they became unrecognizable. About the only similarity left after a few years was the base size and the bobbin and hook area. If you stare at pictures of machines every day like I do you'll see basic clones with more square modern looking sides and lights cast into the housings.
Rodney