Officers, being of the privileged class, were expected to provide themselves with comforts and equipment denied to other ranks. The waterproof or "trench coat" was an article developed during the First World War. British and Canadian Army Dress Regulations of the 1930s did not specify a pattern of waterproof coat, save that it was to be drab in colour. During the war it appears that the coats became more or less standardised and were an item that could be purchased privately or supplied by Ordnance stores upon repayment.
All buttons are in leather. From examples seen, it appears that if rank insignia was worn, they were in metal.

Ordnance supplied Trench Coat. Each shoulder has a cape flap secured by a single small button. The coat has eight large front buttons, the top two being concealed by the cape flaps.

Typical label on an Ordnance issued trench coat.

Another pattern of Ordnance supplied trench coat.

Label on an Ordnance supplied trench coat. Note the plaid wool non removable lining.

A tailor made private purchase No. 2 trench coat. The coat has a ten button front and the collar is closed with two hooks and eyes. There is a single cape type flap.

Shoulder and collar details.

Waist details showing the detachable cloth belt with leather covered steel buckle.

Tailors tag sewn into the back of the lining.

Cuff detail showing the adjustable strap and buckle.

An example of a removable Camel Fleece lining for the No.2 Trench Coat.