Thanks for this information.
My specific case was a pure wafer with no lugs, or ears/cams. The reason I was interested in this particular valve is that it was available quickly, and it isn't that easy to find a DN 600 valve quickly.
I have spoken to the supplier again and yes he advised this...
I am looking for clarification regarding the requirement for a clearance or overlap between the outside diameter of a wafer check valve and the diameter between bolts (which in ASME B16.34 is described as the "circumference of a circle inscribed through the inner tangent points to the flange...