Pictures are of unknown organism but possible from small mammals. The relationship between the trachea and esophagus can be seen in the third one. The “C” shape cartilage ring that form most of the trachea and the trachealis muscle at the back can be seen in some of the pictures.
Trachea (TM: ~2.5x, picture taken with a Nikon Coolscan V slide scanner)Trachea (TM: ~2.5x, picture taken with a Nikon Coolscan V slide scanner from a damaged slide)Trachea and Esophagus (TM: ~2.5x, picture taken with a Nikon Coolscan V slide scanner from a damaged slide)