Nice! That’s a beautiful helmet.

I have a gut feeling it isn’t time related. Triangles must mean something. Why didn’t he do tally marks? Months and then crossed out, and why in groups of 24? So much speculation here. Any other thoughts on what it could be besides time?

Majority of the leaflets have codes for each different leaflet with some having "EUSAK" (Eighth United States Army Korea) on them.

The following KW propaganda leaflets were brought back from the War as he was assigned to one of the 2nd Log Cmd supply depots at the beginning of the war.  

A great USN fixed bale M-1 Helmet, denim laundry bag and Anarac jacket.   Helmet named to Roberts, J.O, S 1/C  579-xxxxxx, last part unreadable.

My guess is......... 49 tick marks.... 49 weeks...... ?

These pictures were taken when my 7th SFGA, Co D, B-team had cross training around February 1968.  Back then, cameras to take pictures were not a problem.  The first picture shows the regular crimpers/cutters and dynomite.  The block explosives is C-3. which was replaced by C-4.  The second picture shows the sheet explosive Flexl-X.  The third picture shows the M-3 Shape Charge with stand., along with a one-pound block of TNT, and, in the background, a 10-cap blasting machine.  The last two shows the before and after detonating the shape charge.

Sorry, I can't make out the markings.  They appear to be scrubbed.  Perhaps reworked or refurbished?