Hey Martin, how's the build coming along? you got me curious about the mark! It does seem to be an 1967 special feature, my engine (no. 1946) has the same mark on the RH side.
The lighting is pretty bad so you'll need to check the full size picture to see it. Your casting mark does seem to be a bit ''higher'' than mine

Snap — I reckon we have the collectable crankcase equivalents of 750/4 KO if not so well known or obvious but I can hear the auctioneer spruiking up these “first edition “ cases, possibly gearbox case too, was def 1st and 2nd gen 4 speed, maybe more, it’s one to see if the trainspotters know their stuff. I’ll make some enquiries in Mandello, story shouldn’t be hard to find. There are a few bolt on differences to 68 but this says production ramped up.
Cylinder heads (single springs, small valves & 36mm ports) a different casting too but these on all 700’s afaik so appear to have been mixed and matched with early / late crankcases in traditional Guzzi style.
Hope to finish engine measurements this weekend but bike won’t be up and running till September, maybe October, about to go on trip for month or two, will post in other thread as I go.
This one for oddities from factory