Helpful refs, thanks again JDT. There's a variation on the "eyelet" style where the threaded hole is surrounded by a a raised "ring" which is more common in the Bianchis (and others) that I've seen in person which use this style DO.
The fork may have a Cromor decal on the blade(s) which does not necessarily mean the frame is Cromor. The 27 seatpost size is a bit curious, normally that would point to an SP seat tube, but don't think this is the case.

Other bits that could be clues are the (allegedly) BSA BB threading, if you just measured the BB shell at 68mm that may not be enough, did you read "1.37 x 24tpi" on the cup(s)? . When/if you get to it the DS cup will be LH threading, even if the cups bear no markings.
And the seat stay caps are vaguely familiar but I cannot put a name to them, however they ring a faint "Italian" brand bell..something well known and NOT Colnago/Colner...but possibly Cornelo...which could make a Benelux connection...