Oval Framed Photograph - Approx 100+ Years Old? (from my research)

I SO MUCH would appreciate being able to find out more about these. What types of photos are these? Their approximate time periods? Where they may have originated from?  The rectangle frame with 3 photos has a stamp on the back I cannot decipher which may help identify it. I have included a close-up photo.

I am not trying to sell these but am always open for consideration should there come an interested party. Thank you so much in advance. I crave this knowledge!! : )

Good