There are a handful of these that also come in a silver back that are not Electric Diamonds. Not all cards have this variation. I discovered this as a kid. I have silver backed versions of#93 #99, #103, #113, #123, #124, #141, #174, #225, #266...I just found this list online of known silverback versions...

58, 59, 60, 68, 71, 73, 75, 81, 83, 84, 86, 89, 92, 93, 97, 99, 100, 102, 103, 105, 113, 120, 123, 124, 137, 141, 151, 157, 160, 166, 171, 174, 184, 187, 195, 224, 225, 237, 238, 239, 246, 250, 259, 261 & 266

There are a couple that I have that are a copperish gold back that were likely a ink printing variation. However the Silverbacks are a bona fide variation.

This is one of the first sets I can remember from my childhood. I was pretty little and rough with these cards, so they are not in the best condition. But still one of my favorite designs for the nostalgia.