Can you identify the markings on this Mills cartridge belt?

[douglas]

I have had this Mills cartridge belt hanging in the closet and every time I open the door I am staring right

at these markings with no clue what they are!!

There are two sets of markings, one set on one end, 77 Z YY and the other more in the center, 840. 

I will post some photos.

 

[douglas]

Here is another photo:

 

[douglas]

And a photo of the belt:

 

[douglas]

The last photo of one of the metal tips: