It looks like a Model 27 or 28 just from looking at the rear of the machine. I have several of them and I have not seen that type of inspection plate before so I am thinking it was replaced with another manufacturers sometime in its long life. The 28 is a 3/4 machine and the 27 is full sized. The bed length on a full sized machine is just over 14". The bobbins can be found at Hancocks or Jo Anns and they will look like little barbells, and it will use the standard 15x1 needle.
Either way you have a nice piece of history in your hands and if I were you I would pull the motor off of it slap it back in the treadle and make a quilt with it. :thumbup:
Billy