The Rangefinder version of the Baby Sibyl was brought out in 1939. Very few could have been sold as it is now extremely rare. It is essentially an ordinary Sibyl to which has been added a rangefinder running vertically along one side. The coupling is quite simple, a lever is passed from the rangefinder housing to the inside of the body, this touches the lazy-tong strut which moves during focusing and so moves the lever. By 1939 few Sibyls were sold, they looked out-of-date and were expensive. The price was £21.0.0 which was £3 dearer than the ordinary model. The position of the focusing lever is not good, the rangefinder tends to be obscured by the hand.

There are minor differences in the rangefinder windows between examples. Later examples have a much narrower lower window than shown here, the upper, circular, window also differs slightly in size.