The Treble Patent marks the boundary between the older Kinnear pattern and the newer 'Field camera' design that was to remain popular to the end of the Edwardian period. The camera continued to be called the Treble Patent even though there were more patents associated with the camera.

Early models were made by Billcliff, the McKellen advertisement in the BJA of 1886 states that the camera is now made in McKellen's own premises, the Billcliff advertisement for 1886 states that he is the maker. Improvements were made to the camera in 1886; the original method of attaching the front standard forks to the inner rack was replaced by pinions, the bellows were less tapered allowing a larger lens opening, the method of fixing the dark-slide was also altered. Advertisements stressed the camera's lightness and its low price.

This example has the improvements introduced for 1886 and, from the address plaque, must date to no later than 1887.

The early (1884) patents associated with the camera are:

• Having a turntable in the base of the camera and so dispensing with the tripod top. There was no hole made in the baseboard so the lens had to be removed from the lens panel (Underwood's patent of 1885 included a hole in the baseboard).

  The image, far right, shows the early form of tripod fixing.

• Pivoting the lens board enabling it to swing forward onto the baseboard whilst the front standard swings backwards when collapsing the camera. Two catches on the camera front, one fitted to the lens board the other to the struts, fix the lens board to the struts, these are moved out of the way to tilt the lens board when closing the camera. On early examples the front standard is fixed to the focusing frame by two large hinges set at the front of the camera, later the front standard swivels on trunnions.
• Having an inner sliding frame for focusing, the frame is moved by a rack and pinions at each end of the frame. This was not a novel feature, nevertheless it made it into the patent.

  The image, right, shows the stop fitted to early models of the camera, it limits the focusing to 'single-extension', the spring on the camera bed is then raised for double extension. This was later replaced by a fixed stop which stopped movement of the focusing frame at the limit of double extension.

• Horizontal swing given to the back by pivoting it to plates that move along each edge of the baseboard. Spring clips lock the swing back in the neutral position, these are similar to those fitted by Billcliff to Thornton's Tourist camera.

The turntable and the swing back were optional, aluminium binding was also available.

This example has the early, pre 1886, front standard fixing and tripod fixing.