Japanese ammo boxes

Hi, I’m new to the board. Thought I would try to get some info on a mystery line on japanese ammo boxes.
This is a photo of 7.7mm (left) and a 6.5mm ammo boxes :

We have a translation :

6.5mm box :

  • San-pachi shiki ju jippo (Type 38 rifle live cartridges)
  • 16 Tsuchinoe (This marking is yet to be deciphered but could be the year of powder manufacturing)
  • 3082 / 273 / 201 (lot numbers)
  • Showa 17.4 (April 1942)

7.7 mm box :

  • Kyu-kyu shiki futsu jippo (Type 99 ordinary ball live cartridges)
  • 16 Tsuchinoe (same as above, unknown)
  • 303/(30)/13/269 (lot numbers)
  • Showa 17.7 (July 1942)

If anyone could help us with the purpose of the “16 Tsuchinoe” we would be greatful. XX Tsuchinoe is on about 85% of the boxes that we have looked at so it’s use as a calender sign is suspect.
Any info would be great!
Thanks to 03man for the photo and Edokko for the translation.

vfp63: Please send me a PM regarding your question about the 1945 Ordnance Department’s work on Japanese markings. Thank you. I am leaving in a few minutes and will be gone all of today, but I will answer it as soon as I can. John Moss