My crica1980 Ofmega CXs were ISO, as were the Bianchi-branded 1990s Ofmegas with which I replaced them. If your spindle is definitely ISO, you won't hurt anything by test-fitting. If the cranks slide too far down the taper, they are JIS. The converse, attempting to seat a smaller-taper ISO crank onto a JIS spindle, is considerably trickier and riskier, because one has to judge how far the crank is seating and risks splitting the end of the crank by overtorquing the fixing bolt.
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"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069