Originally Posted by
big chainring
Maybe a Bob Jackson?
Suppose that it could be a Bob Jackson (AKA JRJ or maybe even one of his Merlins) but no clue that gives away anything. JRJ/Jackson/Merlin certainly did use Nervex pro lugs but by around this frame's era they were employing more Prugnat lugs, typically. And not sure they ever used EDA BB shells. I saw something that may be a clue: the serial numerals on both BB shell and steerer have not rusted (much) compared to the "R ^ M" and I agree that looks more like an inverted "V" than an "A", on the BB shell. Leads me to think it was done after the chroming (not before) so more likely stamped by an owner than a builder.