TR4 and 4A original parts books state that 604917 is the Right Hand Hinge and 604918 is the Left Hand Hinge.
The TR250 and TR5 original parts books state that 614917 is the Right Hand Hinge and that 614918 is the Left Hand Hinge. The change from '0' to '1' must have been a typographical error on the part of the Standard Triumph publications department as the numbers are otherwise too close for comfort!
On top of that some suppliers parts books over the years have managed to transpose the numbers to add to the confusion, however, we are confident the above is correct and keep 604917 as a Right Hand Hinge. As 604918 are not available separately, you must buy a pair which we keep as 604917/8. This is because the suppliers of the after-market parts will only supply in pairs. We have a stock of original Triumph hinges, but Right Hand only.