Looks like a 918 to me as well. That said I can not offer any info as It is beyond what I have seen.
These tags were typed by women in the Steno pool. She may have typed that while being distracted and left it just to get it off her desk.
Thanks, I was kind figuring that at this point. I did read that on rare occasions the week was represented by a number but this one doesn’t really fit that type of pattern either. Thanks again!