Dampner question

I dont think I have found a solid answer yet for this question so Ill ask again.

My 86 Dampener has three hash marks around its circumfrence. Pict 539 ( first pict ) shows their location.

Pict 540 ( second picture ) is the mark I was using to set timing too cause it was the mark that went the farthest thru the dampener. It is registered on three of the rings.

Hash marks # 2 and 3 are only on two of the rings as can be seen in picture 541. ( 3rd picture )

Going to my 83 parts truck the dampener is a bit different but again 3 areas are hash marked around circumference of the dampener.

Pict 544 ( 4th pict. ) shows the marks on only two of the rings. Pict 545 and 546 show the marks on only the first ring. ( 5th and 6th pict )

Can someone tell me what all these marks are used for?