Looks like a very well made bow, probably from the 1940's.Yep, looks like sinew backing the yew. Without any markings or a provenance, it would be hard to attribute it definitively to any known bowyer. Still a lovely bow, and an absolute bargain for $20.
Looks like it could still be a shooter, with careful bracing, and exercising. If you don't already know the details on how to attempt this safely, let us know and someone will chime in. There is always a risk with and old bow, even in an apparently good condition.
Hamish.