Help with markings

I posted this on another forum but haven't gotten any hits. Can someone tell me what the markings in this picture indicate?

I'm speaking of the 1:2 and sawtooth marking on the lower right of the blade just in front of the guard. This is a M1905 blued bayonet dated 1918.

Thanks!

Robert

It is the partial eagle head stamp for US inspection with the inspectors number.

Thanks....I had suspected something like that but am a bit puzzled by the fact that I do not see that on any of the other M1905 bayonets I have in my collection. Was this a WWI feature or can it be nailed down to a specific time period or other activity?