From 1981 to 1987 the obverse and reverse of the 8 g gold coin were the same as that of the 15 g silver coin. The exception being in 1985 when the reverse differed. 1987 seems to be special: (1) both the 5 oz.
Between 1981 and 1987, the front and back sides of the 8 g gold coin were congruent with those of the 15 g silver coin. However, in 1985, the reverse side diverged. Notably, 1987 stands out as a singular instance: (1) both the 5 oz.