I think the OP's bike has the crankset and BB of a Raleigh Gran Sport, or maybe a Super Tourer, which came stock with the chainguard and extra-long c'ring bolts and spacers and a 125 mm or so spindle rather than the usual 118 mm spindle Stronglight used for doubles. Chainguard goes where the big ring should go, 52T in the inside position, 40 or 42T with spacers further inboard where a granny ring would go if only the BCD was smaller than 122. I don't think I've ever seen this set up on anything other than Gran(d) Sport(s) and Super Tourers.