I got this from a 1988 Falcon catalog. 453 is butted Chromalloy-M like 501. It is heat-treated and cold worked. Tensile strength is 802 N/mm2. Gauge is 1.02/0.81mm. It looks like 453 was just the 3 main tubes. 501 had all the tubes and the gauge was different.
Leonard Bulger
Foggy and icy Ann Arbor