The m8 would be close to 40 years old now. It was a premium model in the 6x range, better than the x36 in light gathering, eye box, eye relief and more expensive.
About 15-20 years ago, there was a step Change in lenses coatings led by the Europeans. This and similar technology filtered through the industry.
I think this what you are seeing in the scopes you are comparing.
The old m8 are good reliable scopes. Newer Model 6x42’s have vx3 lense coatings BAT4? And click adjustments.
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