This is superb. Is the tubing MAX? Kinda looks like it, maybe not the chainstays (obviously not the fork). Listing just says 'Columbus multi shape tubing'.
MS was a, short-lived, tubeset so perhaps that's what it is: every tube was a different shape.
That would explain why there's no "Roberts" in the BB shell, nor an "R" in the fork crown as he wouldn't have been able to use his usual shell and crown.
Very nice Roberts track
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F332543552718