Marvin should be able to tell you the historically correct size but I think that the 2 13/32" is the correct size if memory serves.

Thanks for the info. I'll contact Marvin tomorrow to confirm

The two choices from Marvin are a result of matching two different Marvin Ultimate Double Hung checkrail sizes with a Marvin Ultimate Casement for the purpose of achieving egress in a bedroom on an elevation that has mostly Double Hung's. That explanation probably doesn't make much sense to most but what I am saying is choose the one YOU like. There is nothing "historically correct" about either.

Spoke with a Marvin rep and will leave this here for anyone else that has this question.

To get the double hung look on casement windows, Marvin uses 1 15/16” for their clad exterior windows and 2 13/32” for their wood exterior windows.

They did point out that the widths close enough that either would likely work.

What is the width of the grill between the glass and a Marvin essential window?