1655/1675 case internal rings - purpose and dimensions?

[jam_27]

The picture is from the web (ebay listing) of a 1675 case.
I have marked the internal rings as 1, 2 and 3.
My understanding is that the the dial sits on 1 and the movement holder ring gets held by 3. Is this correct?
(Dont know if there is a movement holder ring in a gen 1655 or 1675)

Also what purpose does 2 serve?

Could someone share the diameters of these three rings?
Gen case or milk case or Vietnam case,any would do, i just want to get an idea and understand.

 

[alligoat]

#1 looks awfully thin to be the dial seat, so maybe #2 is the dial seat and number 3 would be for the hold down tabs. Between 1 and 2 might be the rehaut, sometimes referred to as the chapter ring.
A gen movement is around 28mm so it doesn't need the spacer ring.