M5/9 8 -o- 20
M = Motor Wheel Corp.
5 = plant #5 (in CANADA) anyone what city/province?
9 = 1969
8 = August
20 = day of month (Wednesday 8/20/69)

MDLB Y4A415
MD = plant - Goodyear Tire Plant Gadsden, AL
LB = size - E70-14
Y4A = type - fiberglass belted w/RWL "GOODYEAR POLYGLAS E70-14"
415 = date - 41st week of 1975

& the wheel appears to be: part # 2660312 (4" bolt circle, 14x4.5")