McInnes-Dobbie steam engine indicator

McInnes-Dobbie steam engine indicator, a chromium steel valve, a varnished mahogany rod component, a balsa triangular component, and an information card for ‘The McInnes-Dobbie steam and gas engine indicators’, by McInnes-Dobbie Limited, London, England

In this steam-engine indicator, which is an improved form of one patented by Mr. T. S. McInnes in 1887-8, a non-conducting vulcanite sheathing on the cylinder and other parts, allows the operator to manipulate the instrument when hot and to change the spring without discomfort.