Possibly the smallest interchangeable-lens SLR camera ever made, the Pentax Auto 110 took 110 film (obvs.) and was manufactured from 1978 to 1985. Sadly, my example is slightly faulty (the film transport mechanism slips sometimes). The 110 Auto is now quite expensive and collectible these days, but I bought mine a long time ago and it cost me next to nothing. I love small cameras like this. Infact, most images on this website were taken with this camera's spiritual successor, the Pentax Q!