Glass Plate Negative

I have this glass plate negative of my grandfather and his mother. Although I also have the photo, I decided to see if I can get a photo from this.

I first scanned it with my Epson printer/scanner, then opened it in my really old Adobe Photoshop Elements program.

There I selected the photo and went to Image adjustments - invert, and got this...

 

 

 

It is actually a little more blue looking.  I then went to Enhance Colour and removed all colour. Then I played with the colour variations and brightness levels until I got a sepia look to the photo.

 

 

 

 

Not knowing anything technical about photography (I'm a point and shoot photographer) I wasn't expecting very much, so I am very pleased with the result.

 

I am intrigued that the photo must have been taken through some sort of frame?