This is a large pattern, open scale marine barograph introduced by the Canadian Meteorological Service in 1957. The scale is from 960 to 1040 millibars, ie, 80mbs rather than the usual 100mb range, creating an even more detailed record. The large drum has a revolution of just over 3 days, presumably designed for crossing the Great Lakes and ideal for the crossing the seas around the UK. The movement uses the tried and tested external spring mechanism developed by Richard Freres some 60 years earlier. The spring was incorporated into a totally new design including for marine use by the highly respected W.E. Knowles Middleton and is referenced in his comprehensive volume entitled 'The History of the Barometer' - see extract. He refers to the 'construction affords a convenient zero adjustment and a means of making time marks without touching the pen arm. A slotted link permits transport by air without danger of straining the mechanism'. 
The 'piston' damper system on this instrument is the earliest I have seen on a barograph.
Apart from marine use the instrument is perfect for the study and recording of minute variations in barometric pressure. The hinged plexiglass lid has a minor chip in one corner and the lid clip mechanism does not function.
Comes with approximately 190 correct charts and a fresh bottle of recording ink.
345mm wide x 155mm deep x 245mm high