These autographs are relatively inexpensive on ebay, but the seller seems to have a good reputation. (I couldn't find anything negative online about the seller or any posts on this site.) There doesn't seem to be any official authentication.
The Barbara Stanwyck has a decent chance of being genuine if it is live ink. Here is a study of her signature. The 5x7 photos have a reputation of secretarials during this era although this one may be genuine.