I believe this is an authentic full frontal nude of Raquel Welch, from around 1970, backstage at a fashion show, in Las Vegas, or perhaps from her TV special Raquel! I've had a copy of this since July, 2003. Here's a cropped version, enlarged to 400%:
I think you can see it full size, if you save the picture, or click on the attachment. It doesn't look photoshopped to me, and finding a different model with those measurements would be difficult.
No, the attachment is not as large as the originally uploaded image file.