Here is a very similar example of your lock, which was made at around the same time, as the serial number is close. The bolt is marked Chubb, which confirms that your lock is also by Chubb. It also has H.S stamped near to the name. The curved end of the bolt suggests that it was used in a wheel type locking mechanism. Your lock is unusual, as it has a bolt that locks in a diagonal direction. Could this be to save a small amount of space, in the case of a small door, or is there another reason why they did not want the bolt to move in the usual vertical direction?
One interesting point is that the bolt stump has a groove in it, but the levers do not have corresponding false notches. If these locks were made at the end of, or shortly after the First World War, it may be that Chubb were returning to normal production, and either using levers they had made for other locks, or wanted to reduce producion costs, therefore omitting the false notches.
A modern 8 lever Chubb detachable bit key (approx. diameter 6.5mm) fits into my lock perfectly, but will not turn, as the bit is slightly too long for this 7 lever lock. This lock may have had a detachable bit key. The bottom of the barrel and curtain has been made narrow, to avoid it touching the bolt lath, which probably would not be necessary for a usual gauge key. This may be an example of Chubb using the same lock body, bolt, levers, etc. for detachable and normal non-detachable type keys, by simply changing the barrel and curtain, and key hole size. Could you tell me what the diameter of the key to your lock would be?
