Antique brass photographer's image framing loupe made in London by Adams and Company. These were used by photographers before they set up their equipment to verify that there was an image worth photographing. More recently a device similar to this would be used by photographers using rangefinder camera (you don't see the actual image area the way you do with an SLR or DSLR camera).
1 7/8" deep. Circle for viewing is 1 3/4" diameter. Base is 1 5/8" diameter. Early1900s? 2 lenses; not the ground glass type.
My grandfather was a New England photographer.
NOTE: The image showing a view of the two separate pieces also shows a paper matte with a cutout for the film type my grandfather would be using that day. I believe he had a number of these mattes that he used for different film sizes.