I'm not convinced there ever was a dedicated 7 speed chain.
of the 3/32 chains, the wide/cheapies can be used up to 6 speed (but not compact 6), the standard non-narrow is used for anything up to 8 and then there are dedicated 9/10/11 speed chains. (I'm basing most of this on having used sedis/maillard/sachs/sram stuff). Perhaps shimano, campag and some other chain makers did do a dedicated 7 speed??
Wippermann claim the chain in question does 5/6/7sp blocks but is a mite too wide to run on 8. Might have an old 8sp Powerlink in the shed to try a dry run....
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