As some of you know, the display back on the cal. 861/863 movements require the use of a spacer which is not required with the 1863 movements. This is due to the change in the design of the movement holder ring which was incorporated into the 3572.50/3573.50/recent LE's with commemorative display backs.
The difference in the rings is shown in these photos with the 1863 ring on the right:
The design of the 1863 ring allows the display back to screw down flush against the ring so that no spacer is required to hold the movement in place. These 1863 rings are available from:
as part number 079LC086108.
I used one of these rings for PW2 and have used one on my 3592.50 to eliminate the flimsy metal spring spacer. This redesigned ring provides a more secure fit for the 861/1861 movements when using a display back.
Unfortunately, these will not work with the cal. 321 movement nor will they work with steel backs.