Filter adapter ring

[guy_boily]

I am using a Heliopan 67/86 , .45ND centerfilter on a Schneider 90

f8 lens. It is being used on a pano 617 camera. I have two X-Pro ND

grad filters with a filter holder. I need the X-Pro adapter ring

that fits on the 86mm outer thread of this filter. The suppliers

note that it comes in two thread pitches, 0.75 and 1.0 mm. Does

anyone have any idea what thread pitch this filters has. I have a

metric tread measuring tool but there are one maybe one and a half

threads, very hard to get an accurate measurement. Thanks for any

response.

Guy