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It is probably a machine made in Japan in the late 50s or sometime in the 60s. Likely on the underside of the base you will find a JA or JC number stamped or stenciled. If you find that you might take a look over here
http://www.doubleveil.net/zssmp/resources.htm
Where there is a collection of JA/JC numbers and details related to them (scroll down to the 2nd 1/2 of the page). This might help pin down some information.
Otherwise you should consider it to be a Class 15 related Japanese machine, meaning it is a straight low shank (or it looks to be from the picture) and likely takes Singer Class 15 bobbins, uses a "1 o'clock" (likely) Class 15 bobbin case, and uses 15x1 needles. The bobbin slide plate is missing in the picture, if you have it that's good. If not, it could be one which has a spring clamp on each side of it to grab the base, or it hinged to the needle plate and was broken off. There can be some variation in these, but if you need one I would look for one with the spring clamps.
Please come back with questions as you start to work on it, people here are great about helping if they can, I've learned tons reading posts here, and asking questions.