Pentax was the first manufacturer to show an early prototype 35 mm behind-the-lens metering SLR camera, which was named the "Pentax Spotmatic". The camera was shown at the 1960 photokina show. However, the first Through-the-lens (TTL) light metering SLR on the market was the 1963 Topcon RE Super, which had the CdS metering cell placed behind the reflex mirror. The mirror had narrow slits cut into the surface to let the light reach the cell providing average metering. Late in the following year, a production model of the Pentax Spotmatic was shown whose CdS light meter cells were on the pentaprism, reading the light off the focusing screen providing average reading, yet keeping the Spotmatic name, but now written in one word. Another clever design appeared in 1965, the Canon Pellix employing a pellicle mirror that is semi-transparent, placing the meter cell on an arm swinging into the lightpass behind the mirror for meter reading.