Tiffen 801 retainer ring ?

I have here on my disk:
* a TIFFEN 801 RETAINER RING MADE IN U.S.A.
* a ring with just the tiniest bit larger outside diameter,
*apparently* the same threads -- either one can screw into the other --
but no markings whatshoever.

They came in two boxes:
* TIFFEN Lens Accessory 801 RETAINING RING
* TIFFEN adapter ring 57 SS-8

The first ring and the first box seem to match each other.
I have no idea about the second box and the second ring.

Does anyone have any idea what these are, or are supposed to do?

Thanks,
~ Scenic Man ~

OOP!

I wrote:
I have here on my disk:

I should have written:
I have here on my desk:

dEsk, not dIsk

TQ