Hi Mark,
Glad you have come back to your post. Been thinking about your Knife, I reckon it's an early 1939 (pre september, outbreak of war) with pressed leather grips. Bexoid grips were replacing pressed leather in 1939, although pressed leather was still used into ths 40's, either old stock or when bexoid was not available. the other reason I think it's pre september 39 is the clothing code number. I believe this code was not, or was rarely used during the war as the army changed from professional to conscript and the large volume of knives being made meant that they were issued generally rather than stamped for a specific soldier.
The clothing code may also explain the lack of a date stamp, as the date of issue would be the same as the soldier's enlistment date which would be on record.
Is SKS77 which is stamped on the blade clearly legible? The reason I ask is that the makers mark should be clearly stamped on the blade or can opener, sometimes on both.If it is a makers mark it is not one I can find, but I am not familiar with knives of this type made outside of Sheffield, and I believe afew were manufactured in Birmingham and London, so it could be one of these. The only two I am aware of who used initials are W&S.B. and J.B&S both of Sheffield.
The broad arrow stamp which appears to be missing from your knife was a standard patern but not a standard size. the size varied depending on which depot it was stamped at. Whereabouts on the knife it was stamped depended on where there was space available and presumably also on the guy who was stamping lt! Some knives were not perfectly stamped, especially when stamped on the spike. The spike on your knife appears to have been well used, and if it had been lightly stamped there it could very easily have been worn off. Some were stamped on the tang very low down, and again this could have worn off.
Now this last bit is pure guesswork, but bear with me! There could very easily be an Indian conection. In 1939 India was still part of the British empire, and there was a large British military presence there. Your knife could very easily have travelled there as part of the kit of a soldier posted to India, and have ended up becoming the property of a sailor based there. If the knife arrived in the USA via an Indian ship or sailor, Whoever bought it would quite rightly say it was probably Indian navy. Most people who own an old knife have a story to tell about it!!
So in conclusion, far from being a dissapointment, I think you have a very rare and interesting piece of history there my friend, and if you ever want to get rid of it I will gladly give it pride of place in my collection!
it does look like a typical WWII model. What are the scales made from? 
s-k
