Can you post a picture?
The model number is probably on a little plaque on the right side of the pillar of the machine.
Is the bobbin case perhaps in the box of attachments? You can buy vintage replacements and modern repro replacements for the bobbin case. Jenny at Sew Classic is a really terrific online seller and she carries a high-quality modern repro for about $40.
http://shop.sew-classic.com/Bobbin-C...-SCBC45751.htm