I think it might be the ABU 30.
They made the 12, 20 and 30 for a bit heavier fishing.
Nicked the table below from a Vintage Reels Forum. *) gives the line capacity for Mono, dimension in mm.
Type Gear Ratio 0,35*) 0,40*) 0,45*) 0,50*) 0,60*)
Ambassadeyr 12 1:4,2 600 m 450 m 350 m
Ambassadeur 20 1:3,41 620 m 500 m 400 m
Ambassadeur 30 700 m 550 m 400 m
Seems the formatting is a bit off, but for 0,45 it's 350m/500m/700m, should be enough to interpret the tabel (I hope

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