Originally Posted by Kontact

Incorrect. The chain you are talking about is a modern 8 speed chain that is sold as compatible with 6 and 7 speed as well.

But as is clear from my post, original vintage 6 speed chains were wider than both 7 speed and the even narrower 8 speed chains. 5 and standard 6 speed chains were 7.8mm wide for the 5.5mm cog spacing, while Ultra 6 and 7 were 7.3mm for 5mm cog spacing and Shimano 8 is 7.0mm chains for 4.8mm spacing.