Could simply be a metal fatigue step inside the gauge. It works on thermal cycles.

found this post on hybridz, so guess a K11 no marking is still a good high volume hitachi

https://forums.hybridz.org/topic/98987-l6-oil-pump-differences/?do=findComment&comment=1179425

 

found this post on hybridz, so guess a K11 no marking is still a good high volume hitachi

https://forums.hybridz.org/topic/98987-l6-oil-pump-differences/?do=findComment&comment=1179425

 

That k11 pump I fitted to my engine in 2016 is still going strong!