Your machine looks identical to mine! I bought mine from an old lady who used to do alterations and used it for sewing heavy denim. I originally bought it (for £10!) as I needed to repair the handle on a crocodile handbag - which it sewed through, along with two other layers of leather - like butter.
They are brilliant machines, almost completely bomb-proof in construction, and will sew pretty much anything. They even compare well with the very expensive Pfaff machines I used to use to sew the uppers when making shoes.
Do you still have the instruction booklet? mine came with it and it's very useful as they are slightly different to modern machines.