We understand these date to circa 1910. We understand also that this is rare and unusual  having LONDON stamped to the dial as they are normally stamped CHICAGO USA.   

The dial is marked with 'MILES PER HOUR PATENT PENDING', 'SEASON MILEAGE',  'MADE IN USA', 'TRIP', '114602A MODEL NO 11' AND 'STEWART SPEEDOMETER MILEAGE RECORDER STEWART & CLARK MFG CO. LONDON'.   

The speedometer is in good cosmetic condition. Just a few minor dents and scratched to the case.  The nice thick bevelled glass which covers the dial is in good condition and is free from any cracks.    

The needle moves when the gears are turned quickly. However, this is not our area of expertise so we do not know about the mechanisms or functions of this speedometer. Please ask any question, so please know what you are buying prior to purchase.   

Due to it's age and my lack of expertise, this is being sold as seen no guarantees or warranty's.   

The approximate dimensions are: 4 1/4 inches / 10.5 cm across the case, 3 3/4 inches / 9.5 cm across dial, 4 1/4 inches / 10.5 cm deep.