Hello! The sphinx decal was used on a couple of different machines. The easiest way to tell a 127, vs say a model 15, which also had a sphinx decal, is by the two long slide plates to the right of the needle. They will move front to back, whereas a 15 for instance, will have a slide plate to the left of the needle. A 15 will also have the tensioner on the face plate left side, above the slide plate, instead of in front of the operator, like every other machine Singer made (115 not withstanding)
You can still turn the hand wheel to make sure the machine will form a stitch. Though, if it doesn't, it's a bargaining point, since it's very hard to break one of the black heads permanently. The belt and the spool pin can be had easily. If you're in the US, the favorite is Jenny, at Sew-Classic.com. If you're in Canada, please PM me, I can help you. If you're somewhere else, I know someone here will have a recommendation.
Most manuals can be had on the ISMACS.net site.